Journal of Neuroendocrinology, 2013, 25, 980–990 © 2013 British Society for Neuroendocrinology
REVIEW ARTICLE
Neurosteroids and Epileptogenesis G. Biagini*, C. Rustichelli†, G. Curia*, J. Vinet*, C. Lucchi*, M. Pugnaghi* and S. Meletti* *Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy. †Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy.
Journal of Neuroendocrinology
Correspondence to: G. Biagini, Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Sezione di Fisiologia e Neuroscienze, Laboratorio di Epilettologia Sperimentale, Universita di Modena e Reggio Emilia, Via Campi, 287, 41125 Modena, Italy (e-mail:
[email protected]).
Epileptogenesis is defined as the latent period at the end of which spontaneous recurrent seizures occur. This concept has been recently re-evaluated to include exacerbation of clinicallymanifested epilepsy. Thus, in patients affected by pharmacoresistant seizures, the progression toward a worse condition may be viewed as the result of a durable epileptogenic process. However, the mechanism potentially responsible for this progression remains unclear. Neuroinflammation has been consistently detected both in the latent period and in the chronic phase of epilepsy, especially when brain damage is present. This phenomenon is accompanied by glial cell reaction, leading to gliosis. We have previously described rats presenting an increased expression of the cytochrome P450 cholesterol side-chain cleavage (P450scc) enzyme, during the latent period, in glial cells of the hippocampus. The P450scc enzyme is critically involved in the synthesis of neurosteroids and its up-regulation is associated with a delayed appearance of spontaneous recurrent seizures in rats that experienced status epilepticus induced by pilocarpine. Moreover, by decreasing the synthesis of neurosteroids able to promote inhibition, such as allopregnanolone, through the administration of the 5a-reductase blocker finasteride, it is possible to terminate the latent period in pilocarpine-treated rats. Finasteride was also found to promote seizures in the chronic period of epileptic rats, suggesting that neurosteroids are continuously produced to counteract seizures. In humans, exacerbation of epilepsy has been also described in patients occasionally exposed to finasteride. Overall, these findings suggest a major role of neurosteroids in the progression of epilepsy and a possible antiepileptogenic role of allopregnanolone and cognate molecules. Key words: allopregnanolone, epilepsy, glia, hippocampus, neurosteroids, pilocarpine doi: 10.1111/jne.12063
Considering the difficulties in terms of social integration, development of abilities and quality of life, epilepsy represents a serious burden for the society. Epilepsy is a very common neurological problem, with a mean prevalence of 0.52% in Europe, 0.68% in the USA and 1.5% in developing countries (1). Several antiepileptic drugs (AEDs) have been developed to treat epilepsy as a first line approach to this disorder. Approximately 50% of patients achieves seizure remission on the first monotherapy or, in 15–25% of patients, seizure remission can be obtained after one or more additional AEDs. However, 25–35% of patients do not respond to AEDs and are affected by pharmacoresistant epilepsy (1). Subjects affected by temporal lobe epilepsy (TLE) represent approximately 20–25% of all epileptic patients (2). Approximately 40% of all TLE cases are followed by tertiary epilepsy centres, and 73% of these patients requires neurosurgery, representing a large burden to the health system.
Overall evidence indicates that the most frequent type of refractory epilepsy is generated in the temporal lobe, especially in mesial structures. This type of epilepsy is generally associated with a characteristic pattern of damage known as hippocampal sclerosis (3). Common but not exclusive features of patients suffering from TLE are: (i) the historical record of an ‘initial precipitating injury’ during infancy followed by recovery (3); (ii) a seizure-free time interval following the precipitating injury known as the ‘latent period’ (4); (iii) the localisation of epileptic foci in the limbic system, generally in the hippocampus, entorhinal cortex or amygdala (5). Most of these characteristics can be reproduced in animal models in which epileptic activity is induced by the kindling procedure or by status epilepticus (SE) (6). The induction of SE can be obtained by electrical stimulation of limbic structures (7), or by injecting chemoconvulsants such as pilocarpine or kainate (4,8,9).
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The pilocarpine model has been widely used ever since its first description 30 years ago (10). Histopathological findings (11) in the pilocarpine model and its use in studying the efficacy of AEDs (12) have been reviewed recently (4,13,14). The popularity of this model is mainly a result of the rapid induction of acute SE and the occurrence of lesions that are associated with the pattern of reorganisation of neuronal networks similar to that observed in the hippocampal and parahippocampal regions of TLE patients (15). Indeed, mossy fibre sprouting (16), loss of interneurones (17) and ectopic dentate granule cell proliferation (18) are phenomena shared by TLE patients and pilocarpine-treated animals (19). The fact that seizures are poorly controlled by AEDs both in TLE patients and in pilocarpine-treated epileptic rodents provides an additional advantageous feature of this model (20,21). During the latent period, several pathophysiological phenomena occur that are putatively related to epileptogenesis. These events include mossy fibre sprouting, loss of interneurones, rewiring of synaptic circuits, glial cell activation and ectopic cell proliferation (22,23). Because there is no definitive evidence that any of these phenomena are critical for epileptogenesis, it is important to evaluate how they vary in relation to SE duration and, in case of differences, how they could modify the latent period. For example, we have recently shown a relationship between the latent period duration and the extent of induction in glial cells of the rate-limiting enzyme of the neurosteroid pathway, the cholesterol side-chain cleavage enzyme coupled to the cytochrome P450 (P450scc) (24– 27). Neurosteroids such as allopregnanolone are endogenous anticonvulsants that are mainly synthesised in astrocytes, which are highly activated by seizures and brain damage (27). Interestingly, we have found that a longer SE leads to a larger hippocampal lesion and, thus, to a stronger activation of glial cells, which finally might be able to extend the latent period by synthesising seizuremodulating substances such as neurosteroids.
A critical reappraisal of epileptogenesis Epilepsy can be associated with genetic anomalies or brain injuries. Postlesional epilepsies, including TLE, follow a brain lesion and manifest themselves after a latent period, ranging from months to years, which is generally considered as the period of epileptogenesis (28). There is a general agreement on the fact that an epileptogenic process takes place during the latent period (28). However, it is difficult to establish the real onset of epilepsy, especially in patients. Indeed, to establish the appearance of the first, generally nonconvulsive, seizure, we would need to continuously monitor the electroencephalogram (EEG) of each person experiencing an injury that potentially could lead, after many years, to epilepsy. In addition, the latent period of TLE is remarkably variable so that it is almost impossible to define a historical record of epileptogenesis, in that seizures could be initially precluded by the use of preventive drug therapies. For these reasons, epileptogenesis has been mainly defined in animal models of postlesional epilepsy, as in the pilocarpine and kainate models of SE (4,6,8), or in models of posttraumatic epilepsy (29). According to these models, epileptogenesis Journal of Neuroendocrinology, 2013, 25, 980–990
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in pilocarpine-treated rats was proposed to last for a period of 3– 4 weeks, assumed to be completely identical to the latent period (30). However, the use of video-EEG recordings has recently put this view into discussion. Indeed, four independent studies showed that most of pilocarpine-treated rats, monitored by intracerebral (31,32) or cortical electrodes (33,34), appear to be epileptic already during the first week after SE (Fig. 1). These results indicate that the latent period and, consequently, the corresponding period of epileptogenesis are very short or difficult to be determined. Further studies have cast doubts on the classic view of epileptogenesis, suggesting a new, interesting interpretation of this phenomenon (29,35). In particular, Williams et al. (35) hypothesised that the end of the latent period, usually set at time of the first seizure appearance, does not necessarily correspond to the end of epileptogenesis, which, instead, could be a process persisting later and participating in the progressive exacerbation of the epileptic condition during the chronic period. This hypothesis substantially translates the Gowers’ concept of ‘seizures beget seizures’ (36) into the definition of epileptogenesis, as also shown by kindling experiments (6,30). In this regard, several lines of evidence appear to support the view of a progressive exacerbation of epilepsy, at least in patients affected by TLE (30). In the pilocarpine model, epilepsy starts with nonconvulsive seizures (based on EEG monitoring; Fig. 1) that, subsequently, develop into motor seizures (32). Moreover, rats treated with kainate manifest a progressive increase in seizure frequency that can be described by a sigmoidal function presenting a steep increase in the chronic period (35). For these reasons, it has also been proposed that a ‘primary’ (i.e. the latent period) and a ‘secondary’ (i.e. the progression through the chronic period) epileptogenesis could be identified (23,36). However, these views do not imply that epileptogenesis may persist indefinitely. Indeed, clinical evidence demonstrates that, in many cases, longterm epilepsy remains stable or actually warrants cessation of treatment and frequently does not recur after drug withdrawal (30). On the other hand, in patients that do not respond to drug treatment, the mechanisms responsible for drug failure are still largely unclear (14,28). According to the original view of epileptogenesis, it has been proposed that relatively fast and aberrant mechanisms, such as mossy fibre sprouting and granule cell proliferation, probably activated as a compensatory reaction, may be at the basis of the onset of TLE (15,22,23,28). Because these phenomena take few days to be set on, it appears obvious that they cannot contribute to the long-term changes required for a progressive epileptogenesis. Other studies have focused on loss of interneurones as a possible mechanism leading to the onset of epilepsy (37). This is an interesting possibility because the progressive course of interneurone loss has recently received support from experiments showing degeneration of specific interneurone subpopulations in epileptic rats and in human surgical specimens obtained from TLE patients (17). However, the most impressive phenomenon, shown to be quickly triggered during SE induction (38) and to persist in the chronic period of the disease, is neuroinflammation (23,39), suggesting that it is involved both in early and progressive steps of epileptogenesis. © 2013 British Society for Neuroendocrinology
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Fig. 1. Electrocorticography (ECoG) traces recorded from a rat at different moments during and after pilocarpine treatment. Pilocarpine injection induced a stage 5 seizure (A) shortly followed by status epilepticus (SE) (B). The day after the treatment, the rat still presented many (21 in 5 h of recording) severe stage 5 seizures (C). At day 5 post-SE, the rat presented abnormal electrographic activity correlated to mild abnormal behaviour resembling stage 1–2 of Racine’s scale (D). At day 9 post-SE, short nonconvulsive seizures (E) were recorded together with more severe generalised convulsive seizures (F). The inset shows a scheme of electrode position on the rat scalp. LF, left frontal; LO, left occipital; RF, right frontal; RO, right occipital; Ref, reference electrode. Details on electrode implantation and video-ECoG recording are provided in Gualtieri et al. (9).
Inflammation and glial cells in the epileptic brain A growing body of evidence is now supporting a relationship between inflammation and epilepsy. Indeed, activated microglia, reactive astrocytes, local expression of pro-inflammatory cytokines, blood–brain barrier leakage and peripheral immune cell infiltration © 2013 British Society for Neuroendocrinology
have all been observed in human TLE as well as in animal models (39). Accordingly, inflammatory mechanisms are thought to play a central role in the initiation and maintenance of seizures, including those starting in the acute phase during SE induction. Although marked gliosis and inflammation are main features of hippocampal sclerosis in TLE, glial cells have been poorly investigated as possible Journal of Neuroendocrinology, 2013, 25, 980–990
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candidates in promoting epileptogenesis. Because the role of astrocytes in epileptogenesis has been reviewed recently (27,40,41), we focus here on microglia. Microglia are the immune cells of the central nervous system (CNS) and are characterised by ramified processes, with which they constantly survey their environment. Upon any type of CNS injury, microglia become rapidly activated, a process that has long been considered as detrimental for neuronal survival. However, recent findings suggest that microglia display neuroprotective properties in various CNS pathologies. Indeed, microglia have been shown to contribute not only to inflammation, but also to tissue remodelling and repair, as well as to neurogenesis (42). In the context of epilepsy, morphologically-activated microglia have been observed rapidly after SE and they remain activated several days afterwards (Fig. 2), suggesting that microglia play a prominent role in the development and maintenance of the disease. Microglia activation has been correlated with the expression of several pro-inflammatory cytokines such as interleukin (IL)-1b, IL-6 and tumour necrosis factor a (TNFa), which are considered to be responsible for the neuronal cell death occurring after SE (39,44). Cytokines such as IL-1b and TNFa have been shown to increase neuronal excitability in
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brain slices and, thus, might be involved in the development of epileptic activity (39,44). Furthermore, up-regulation of chemokines, such as chemokine (C-C motif) ligand 2 (CCL2), CCL3 and CCL4, as well as of chemokine receptors including chemokine (C-X-C motif) receptor 4, is also observed in the hippocampus of both human epileptic patients and pilocarpine-treated animals. It is assumed that the chemokine system is crucially involved in the recruitment of peripheral inflammatory cells (39,44). Finally, minocycline was shown to reduce microglia activation, as well as the later seizure susceptibility, in young animals (45). Overall, the data point towards a pro-inflammatory phenotype of microglia that precedes neuronal injury and cell death. Microglia are therefore generally considered to play a pro-epileptogenic role. Interestingly, evidence indicating a beneficial role of microglia in pathological brain conditions has been published recently. Indeed, under demyelinating conditions, microglia produce and secrete anti-inflammatory cytokines and neurotrophic factors, including IL10, transforming growth factor b and brain-derived neurotrophic factor (46). Furthermore, microglia have been shown to be neuroprotective in Alzheimer’s disease and ischaemia, and they also promote axonal regeneration and provide instructive signals for
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21 days Fig. 2. Time course of microglia activation following status epilepticus (SE) induced by pilocarpine. Rats are the same described in Gualtieri et al. (17). Microglia activation was followed at several time points during epileptogenesis, using an antibody against Iba-1 (43). During the first 72 h after SE, microglia activation remained circumscribed inside and around the astrocyte lesion, located in the CA3 stratum lacunosum molecolare (white boundaries), illustrated by an antibody against glial fibrillary acidic protein (GFAP; 9). At 7 days after SE, microglia cells greatly increased and activation was clearly observed outside the lesion and even in the CA3 stratum pyramidalis, as also fully displayed 14 days after SE. Microglia activation still persisted at 21 days after SE, even though the lesion had disappeared. Scale bars = 50 lm. Journal of Neuroendocrinology, 2013, 25, 980–990
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neurogenesis (47). It has further been demonstrated that microglia are essential for neuronal protection against excitotoxicity (43). Recent findings also demonstrate that microglia express major histocompatibility complex in absence of co-stimulatory signals, as well as membrane markers of immature dendritic cells, suggesting that their principal function is to stop lymphocytic inflammation and to promote tolerance (48). Evidence for a beneficial role of microglia in epilepsy also exists. For example, the induction of TLE in IL-6 knockout animals leads to a decrease in microglia activation. However, it is also accompanied by an increase in oxidative stress, neuronal cell death and enhancement of the severity of seizures, suggesting that inhibition of microglia activation might worsen epilepsy development (49). Moreover, specific depletion of hippocampal microglia resulted in no changes in acute seizure sensitivity compared to normal animals, suggesting that microglia are not responsible for disease development. In the same study, preconditioning with lipopolysaccharide prior to acute seizure induction provoked greater seizure activity and increased mortality in absence of microglia, indicating that activated microglia may have a protective function during SE (50).
Neurosteroids and the latent period of epilepsy More than 30 years ago, it was demonstrated that the steroid dehydroepiandrosterone sulphate is directly produced in the brain, where it can be increased by stress in spite of orchiectomy and adrenalectomy. These findings led to the concept of ‘neurosteroids’ (i.e. molecules that are directly synthesised from cholesterol in the nervous system) (51). Subsequently, it was found that P450scc, which converts cholesterol to the steroid precursor pregnenolone, was mainly localised in myelinated fibres of the white matter (i.e. in oligodendrocytes), with the exception of scattered neuronal cells that were found to express P450scc in some limbic structures (52). Additional work has demonstrated that the P450scc can be found in neurones of various brain regions, including Purkinje cells in the cerebellum (53) and pyramidal cells in the hippocampus (54). Astrocytes also express P450scc (55). We have recently reported that P450scc immunoreactivity co-localises with haeme oxygenase-1, a nonspecific marker that is expressed at very high levels especially in activated microglia (25,27). In the brain, the 18-kDa translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is predominantly expressed in microglia activated by lesion (56–59). This protein co-operates with the steroidogenic acute regulatory protein (StAR), also identified in activated microglia (60,61), in transporting cholesterol across the mitochondrial membrane. Thus, the presence of P450scc in the same cells provides a complete biochemical machinery to synthesise pregnenolone (62). A complete account of enzymes expressed in astrocytes was reported in a previous review (27).
P450scc and the latent period In models of SE, the massive loss of cells able to produce neurosteroids, as in the case of hippocampal pyramidal cells (4,9,63), or, © 2013 British Society for Neuroendocrinology
alternatively, the activation of glial cells expressing PBR-TSPO, StAR and P450scc could result in a profound change in the metabolism of neurosteroids. To address this hypothesis, we characterised the levels of P450scc immunoreactivity in the pilocarpine model of TLE (24,25) (Fig. 3). In the first weeks after SE, we observed a strong induction of P450scc, with the most significant increase in the hippocampal CA3 region (24,27), both in neuronal and glial cells. However, up-regulation of P450scc in neurones was limited to the first week after SE, whereas the changes observed in glial cells lasted more than 2 weeks and were superimposed on the latent period. The prevalence of P450scc induction in hippocampal astrocytes was clearly appreciated in experiments of co-localisation with cell-specific markers (25,27). Thus, we demonstrated that a key enzyme of the neurosteroid metabolic pathway is up-regulated in unambiguously identified different P450scc-positive cell-types, especially in tissue obtained 1 week after pilocarpine-induced SE (Fig. 3). We also hypothesised that the induction of P450scc was related to the duration of SE because a larger amount of damage follows longer periods of continuous seizures (4,63). Indeed, we were able to demonstrate that P450scc was induced at higher levels in rats exposed to 3 h of SE compared to those exposed to 1 h only (24,25). Subsequently, we investigated the possible influence of the different extent of P450scc induction on the duration of the latent period. During the first weeks after SE, the extent of P450scc induction in hippocampal astrocytes appeared to have major consequences on the onset of stage 5 generalised seizures (Fig. 3B) of Racine’s scale (64) (i.e. the higher P450scc is expressed, the lower the amount of early stage 5 seizures observed). Consistently, together with P450scc levels, the length of the latent period progressively increased as pharmacological cessation of SE by diazepam administration was retarded from 60 to 120 or 180 min (25). This correlation between P450scc induction and the extension of the latent period was confirmed also in immature rats. Particularly, we showed that young (3-week-old) rats exposed to short (60 min) SE presented a more pronounced induction of P450scc compared to adult animals and, consequently, displayed rare stage 5 seizures during the chronic period (26,27,63).
Finasteride terminates the latent period by reducing allopregnanolone The induction of P450scc in glial cells was indeed suggestive but not necessarily predictive of increased neurosteroid synthesis in the brain of pilocarpine-treated rats (61). Therefore, we assessed whether, by inhibiting the enzyme 5a-reductase with the specific and irreversible inhibitor finasteride (100 mg/kg), it was possible to affect the seizure onset in pilocarpine-treated rats; specifically, this procedure provoked an early onset of spontaneous recurrent seizures in pilocarpine-treated rats (24,25). This phenomenon was probably related to decreased synthesis of neurosteroids, such as allopregnanolone, that are able to promote inhibition by interacting with the c-aminobutyric acid type A (GABAA) receptors (65). Finasteride at 10 mg/kg was shown to acutely deplete allopregnanolone without affecting 3a-dihydroprogesterone, progesterone or deoxycorticosterone (66). When, repeatedly, administered at 25 mg/kg, Journal of Neuroendocrinology, 2013, 25, 980–990
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Fig. 3. Time course of cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc) immunoreactivity in rats exposed to pilocarpine-induced status epilepticus (SE) compared to the onset of generalised seizures. (A) Localisation of P450scc-immunopositive cells in the dentate gyrus and CA3 region of the hippocampus, 1 week after SE. Cellular markers for astrocytes (identified by glial fibrillary acidic protein, GFAP), activated microglia (identified by haeme oxygenase1; HO-1) and neurones (identified by neurone-specific nuclear protein; NeuN) were used (27); scale bars = 250, 300 and 125 lm, respectively, from top to bottom. (B) Changes in the expression of P450scc immunoreactivity of glial cells, and the appearance of spontaneous recurrent generalised seizures, are shown during epileptogenesis. Note that seizures appear when P450scc immunoreactivity decreases. Re-elaboration of data from Biagini et al. (24,27).
finasteride significantly decreased both allopregnanolone and allotetrahydrodeoxycorticosterone brain levels (67). We confirmed these findings in pilocarpine-treated rats in a pilot experiment, in which acute treatment with finasteride (100 mg/kg, s.c.) significantly reduced allopregnanolone levels in the hippocampus (Fig. 4); for methods, see Rustichelli et al. (68). To exclude that the modulation of the latent period by finasteride could be explained by other variables, we have tested the effects of finasteride in different paradigms of SE duration and addressed whether 5a-reductase inhibition correlates with the extent of P450scc induction. Consistent with the correlation among SE duration, P450scc induction and the duration of the latent period, in rats experiencing at least 180 min of SE, we observed an early appearance of stage 5 seizures (64) when these animals were treated with finasteride (100 mg/kg). By contrast, the same finasteride treatment was ineffective in rats exposed to 90 min of pilocarpine-induced SE, in which only limited changes in P450scc expression were observed (25). Again, finasteride was ineffective in altering the duration of the latent period in adult (8-week-old) rats exposed to 60 min of SE, which presented spontaneous recurrent seizures as early as 10 days after SE (26), whereas stage 5 seizures appeared in approximately 50% of young (3-week-old) rats exposed to 60 min of SE and treated with finasteride already during the first week of treatment, when P450scc levels were remarkably high. Moreover, no other stage 5 seizures were observed in the further finasteride treatment days, when P450scc immunoreactivity reached the peak level (27). Notably, the experimental groups exposed to Journal of Neuroendocrinology, 2013, 25, 980–990
60 min of SE clearly differed in the extent and duration of P450scc induction, which was markedly higher in the CA3 hippocampal subfield of young rats. Therefore, these findings suggest that neurosteroid synthesis is related to the extent of P450scc induction occurring in glial cells after SE and that neurosteroids influence the latent period.
Neurosteroids and the chronic period of epilepsy Lines of evidence suggest that neurosteroids modulate epilepsy in the chronic period of this disease (i.e. when motor seizures are manifested). Catamenial exacerbation of epileptic seizures, which could be interpreted as a possible evidence of persisting epileptogenesis in TLE (23,30,35,36), provides compelling evidence of the involvement of steroids in this chronic neurological disorder, a phenomenon explained by the influence on GABAA receptor plasticity exerted by fluctuations in steroid production and their conversion in neurosteroids (69). The modulatory properties of peripheral steroids and their relationship with physiological fluctuations in neurosteroids during the ovarian cycle have been identified by analysing the changes in d-GABAA receptor subunit in mice in which seizure threshold was assessed by kainic acid administration (70). It was found that the amplitude of tonic GABAA receptormediated current is two-fold higher during late dioestrus in dentate gyrus granule cells. This change was mirrored by a 43% increase in hippocampal d-GABAA subunit and the two findings were related with fluctuations in progesterone plasma levels. Notably, female © 2013 British Society for Neuroendocrinology
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mice injected with kainate presented a more pronounced latency to seizure appearance during dioestrus (i.e. when progesterone level peaks), and the mean seizure duration was much shorter. These data point to a role of progesterone in producing GABAA-mediated antiseizure effects in the perimenstrual period.
Evidence for a role of neurosteroids in animal models of catamenial epilepsy The characterisation of sexual hormones in in vivo models of epilepsy contributed to clarify the role of oestradiol as a proconvulsive hormone and, conversely, of progesterone as an anticonvulsive counterpart. In particular, oestradiol has been shown to have proconvulsant effects in ovariectomised rodents, to increase audiogenic seizures in a kindling paradigm, and to potentiate seizures induced by the GABAA receptor antagonist pentylenetetrazole (PTZ), and by kainate (71). Lines of evidence suggest that the anticonvulsant effects of progesterone are dependent on its metabolite allopregnanolone. In the brain, progesterone is converted by 5a-reductase to 5a-dihydroprogesterone, which is then metabolised by 3a-hydroxysteroid dehydrogenase obtaining allopregnanolone. Allopregnanolone interacts with GABAA receptors and produces anticonvulsant, anxiolytic and anaesthetic effects similarly to other GABAA modulators, such as benzodiazepines, barbiturates and alcohol (72,73). Following Selye’s seminal experiments on the anticonvulsant properties of progesterone in PTZ-induced seizures (74), consistent results have been obtained in various animal models, including amygdala kindling and the maximal electroshock test, as well as PTZ-induced seizures (71,75,76). The properties of allopregnanolone and its role in mediating the progesterone effects on seizures were demonstrated by pretreating mice with finasteride before testing them in the PTZ model or the maximal electroshock seizure test, in which finasteride prevented the antiseizure effect of progesterone (71,75,76). The critical role of progesterone conversion © 2013 British Society for Neuroendocrinology
to allopregnanolone was also confirmed in genetically manipulated mice deficient in 5a-reductase (77). The role of neurosteroids has been thoroughly investigated in models of catamenial epilepsy, in which periodicity of seizure exacerbation aligns with the menstrual cycle (69,71). Because rodents present an oestrous cycle lasting 4–5 days, to recreate the human condition (78) in a model with sufficient homology, female rats were treated with gonadotrophins to increase ovarian hormone levels (79,80). Gonadotrophin administration produced a sustained increase in circulating levels of oestrogen and progesterone, thus reproducing the luteal phase of the human menstrual cycle. Subsequently, to reproduce the abrupt decrease of allopregnanolone levels provoked by the onset of menstruation, rats received finasteride 11 days after the beginning of gonadotrophin administration. The result of gonadotrophins and, especially, finasteride administration was the sensitisation to seizures induced by PTZ (79). Additional studies were conducted using this paradigm in female rats with spontaneous recurrent seizures (80,81). Female rats were used that became epileptic after having experienced SE. In epileptic animals, neurosteroid withdrawal was associated with a marked increase in seizure frequency. Particularly, by monitoring these animals for approximately 5 months, it was established that they presented around two seizures/day. Seizures were decreased in response to induction of neurosteroids by gonadotrophin administration. As expected, finasteride administration provoked in these rats a twofold significant increase in seizure frequency (80,81). Subsequent extensive experiments (82), based on artificially elevating progesterone plasma levels with pregnant mare serum gonadotrophin/bhuman chorionic gonadotrophin in female rats made epileptic by pilocarpine-induced SE, were consistent with the results described previously (80,81). In detail, progesterone levels reached a peak that was three-fold higher than in control epileptic rats. Subsequently, a subgroup of rats treated with pregnant mare serum gonadotrophin/ b-human chorionic gonadotrophin was exposed to a single Journal of Neuroendocrinology, 2013, 25, 980–990
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whether motor or nonconvulsive seizures (or both) increased, although the overall changes were indeed remarkable: 26-fold more than the mean frequency recorded in previous days (82). Although the effect of finasteride in rats receiving pregnant mare serum gonadotrophin/b-human chorionic gonadotrophin was impressive, a significant effect was also found in control epileptic rats, in which a 11-fold increase in seizure frequency was reported (82). This result was even more interesting because it suggested that seizures were presumably counteracted by an endogenous mechanism dependent on neurosteroid synthesis. To test this hypothesis, Lawrence et al. (82) analysed the response to finasteride by following up the changes in seizure frequency after the finasteride injection in control epileptic female rats. In addition, they administered allopregnanolone following finasteride, in an attempt to replace this putative endogenous anticonvulsant that was abolished by finasteride treatment. In this experiment, it was confirmed that finasteride increases the seizure frequency, as well as that allopregnanolone is able to counteract the finasteride effect.
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Evidence for a role of neurosteroids in patients affected by catamenial epilepsy
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Fp2-F4 F4-C4 C4-P4 P4-O2 Fp2-F8 F8-T4 T4-T6 T6-O2 FZ-CZ CZ-PZ Fp1-F3 F3-C3 C3-P3 P3-O1 Fp1-F7 F7-T3 T3-T5 T5-O1 X1-RF
Fig. 5. Exacerbation of temporal lobe epilepsy by finasteride. Data are from Pugnaghi et al. (87). (A) Time-course of seizure frequency (number of seizures per year) from 1997 to 2012. Seizures are all partial (autonomic and gustatory aura inconstantly followed by oro-alimentary automatisms, language dysfunction and rarely brief loss of contact), except a single convulsive seizure during sleep in 2002 (marked with an asterisk). Top: representation of the time-course of the pharmacological treatments (finasteride, carbamazepine and lamotrigine). It is clear that finasteride withdrawal is correlated with prompt seizure freedom achievement. (B) Electroencephalographic recordings of the patient during finasteride treatment showing left temporal theta activities and spikes (circles) during drowsiness (top) and sleep (bottom).
injection of finasteride. Finasteride was also injected to control epileptic rats with normal progesterone levels. A clear increase was found in the frequency of seizures monitored by EEG and videorecordings in rats receiving the serum. However, it was not indicated Journal of Neuroendocrinology, 2013, 25, 980–990
Catamenial epilepsy is the best example of the tendency of seizures to occur in clusters, a trend generally observed in approximately 50% of patients affected by epilepsy (83) and also demonstrated in animal models based on male rats (32). In catamenial epilepsies, generalised and focal seizure clusters appear to present a pattern of temporal distribution in relation to the menstrual cycle, including a perimenstrual, periovulatory or luteal recurrence (78). It has been estimated that approximately one-third of women with pharmacoresistant partial epilepsy are affected by catamenial epilepsy (78). Progesterone has been proposed for a long time to be an effective treatment for catamenial epilepsy (78,84,85), acting by undefined mechanisms presumably involving progesterone nuclear or membrane receptors, or GABAA receptors (86). However, pioneering work has shown that the antiseizure effects of progesterone are not mediated by progesterone nuclear receptors (75) and, consistently, are prevented by finasteride (76). A clinical case that confirmed the findings obtained in animal models was reported by Herzog and Frye (85). They observed a remarkable increase in seizure activity in a patient affected by catamenial complex partial seizures, previously well controlled by carbamazepine and progesterone treatment, and unexpectedly become pharmacoresistant (85). The reason for the abrupt exacerbation of catamenial epilepsy in the reported patient was the administration of finasteride to treat a progressive type of baldness, thus suggesting that, even in patients, progesterone has to be converted to allopregnanolone to control seizures. Furthermore, we have recently obtained evidence on the existence of antiepileptic effects of endogenous neurosteroids in a women affected by TLE (87). This patient, under treatment with finasteride for hirsutism, was suffering from autonomic and gustatory auras with a cluster pattern reminiscent of catamenial epilepsy, which started at the age of 43 years. Two years later, oroalimentary automatisms, language dysfunction and rare loss of contact recurred, so that carbamazepine was administered to control these © 2013 British Society for Neuroendocrinology
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seizures. After 1 year of apparent relief, a convulsive seizure occurred when she was sleeping. Then, seizures relapsed with a frequency of eight to ten episodes per year, requiring an add-on treatment with lamotrigine (Fig. 5). Nonetheless, seizures were refractory to both AEDs and, on three occasions, they were complicated by fall to the ground. The interictal EEG showed left temporal theta activities and spikes during drowsiness and sleep, although no brain anomalies were found in both hippocampi by magnetic resonance imaging evaluation. At this point, treatment with finasteride was discontinued and seizures completely ceased (87). At present, the patient is still seizurefree with a terminal remission of 7 years after the discontinuation of finasteride. It is probable that finasteride exacerbated seizures in this patient by precluding the synthesis of 5a,3a-tetrahydrosteroids in the brain. This case and the one described by Herzog and Frye (85) support the view that endogenous neurosteroids regulate seizure susceptibility in patients affected by epilepsy and suggest that they may interfere, by synergising, with concomitant AED treatments.
Conclusions Overall, the evidence from animal models and clinical cases support the hypothesis that neurosteroids are major regulators of epileptogenesis. Following a brain injury, critical enzymes in the neurosteroid pathway are up-regulated and contribute to a significant increase in allopregnanolone tissue levels. Increased allopregnanolone levels may oppose to epileptogenesis during the latent period and even for a long time, as observed in young rats, and are able to delay the onset of the chronic period of epilepsy, at least in TLE models. However, a role for allopregnanolone is delineated also in the chronic period of epilepsy because inhibition of 5a-reductase significantly intensifies seizure recurrence, also by limiting the efficacy of AEDs. These findings suggest that allopregnanolone and cognate molecules may be taken into consideration as promising antiepileptogenic molecules and/or add-on treatments in pharmacoresistant epilepsy.
Acknowledgements This study was supported by Pierfranco and Maria Luisa Mariani Foundation (R-12-94 to GC and GB), Emilia-Romagna Region (Region-University Programme 2007-09, grant 1232 to GB and SM) and Italian Ministry of Education, University and Research (‘Rientro Cervelli’ project 17DZE8RZEA to GC). The authors declare that there are no conflicts of interest.
Received 22 March 2013, revised 21 May 2013, accepted 9 June 2013
References 1 Strzelczyk A, Reese JP, Dodel R, Hamer HM. Cost of epilepsy: a systematic review. Pharmacoeconomics 2008; 26: 463–476. 2 Tellez-Zenteno JF, Hernandez-Ronquillo L. A review of the epidemiology of temporal lobe epilepsy. Epilepsy Res Treat 2012; 2012: 630853. 3 Mathern GW, Adelson PD, Cahan LD, Leite JP. Hippocampal neuron damage in human epilepsy: Meyer’s hypothesis revisited. Prog Brain Res 2002; 135: 237–251.
© 2013 British Society for Neuroendocrinology
4 Curia G, Longo D, Biagini G, Jones RS, Avoli M. The pilocarpine model of temporal lobe epilepsy. J Neurosci Methods 2008; 172: 143–157. 5 Bartolomei F, Chauvel P, Wendling F. Spatio-temporal dynamics of neuronal networks on partial epilepsy. Rev Neurol (Paris) 2005; 161: 767– 780. 6 Morimoto K, Fahnestock M, Racine RJ. Kindling and status epilepticus models of epilepsy: rewiring the brain. Prog Neurobiol 2004; 73: 1–60. 7 Lothman EW, Bertram EH, Bekenstein JW, Perlin JB. Self-sustaining limbic status epilepticus induced by ‘continuous’ hippocampal stimulation: electrographic and behavioral characteristics. Epilepsy Res 1989; 3: 107–119. 8 Ben-Ari Y, Cossart R. Kainate, a double agent that generates seizures: two decades of progress. Trends Neurosci 2000; 23: 580–587. 9 Gualtieri F, Curia G, Marinelli C, Biagini G. Increased perivascular laminin predicts damage to astrocytes in CA3 and piriform cortex following chemoconvulsive treatments. Neuroscience 2012; 218: 278–294. 10 Turski WA, Cavalheiro EA, Schwarz M, Czuczwar SJ, Kleinrok Z, Turski L. Limbic seizures produced by pilocarpine in rats: behavioural, electroencephalographic and neuropathological study. Behav Brain Res 1983; 9: 315–335. 11 Covolan L, Mello LE. Temporal profile of neuronal injury following pilocarpine or kainic acid-induced status epilepticus. Epilepsy Res 2000; 39: 133–152. 12 Leite JP, Garcia-Cairasco N, Cavalheiro EA. New insights from the use of pilocarpine and kainate models. Epilepsy Res 2002; 50: 93–103. 13 Tang FR, Loke WK, Ling EA. Comparison of status epilepticus models induced by pilocarpine and nerve agents – a systematic review of the underlying aetiology and adopted therapeutic approaches. Curr Med Chem 2011; 18: 888–899. 14 Potschka H. Animal models of drug-resistant epilepsy. Epileptic Disord 2012; 14: 226–234. 15 Avoli M, D’Antuono M, Louvel J, K€ohling R, Biagini G, Pumain R, D’Arcangelo G, Tancredi V. Network and pharmacological mechanisms leading to epileptiform synchronization in the limbic system in vitro. Prog Neurobiol 2002; 68: 167–207. 16 Sutula T. Seizure-induced axonal sprouting: assessing connections between injury, local circuits, and epileptogenesis. Epilepsy Curr 2002; 2: 86–91. 17 Gualtieri F, Marinelli C, Longo D, Pugnaghi M, Nichelli PF, Meletti S, Biagini G. Hypoxia markers are expressed in interneurons exposed to recurrent seizures. Neuromolecular Med 2013; 15: 133–146. 18 Scharfman HE, McCloskey DP. Postnatal neurogenesis as a therapeutic target in temporal lobe epilepsy. Epilepsy Res 2009; 85: 150–161. 19 Wieser HG. ILAE Commission on Neurosurgery of Epilepsy. ILAE Commission Report. Mesial temporal lobe epilepsy with hippocampal sclerosis. Epilepsia 2004; 45: 695–714. 20 Glien M, Brandt C, Potschka H, L€oscher W. Effects of the novel antiepileptic drug levetiracetam on spontaneous recurrent seizures in the rat pilocarpine model of temporal lobe epilepsy. Epilepsia 2002; 43: 350– 357. 21 Chakir A, Fabene PF, Ouazzani R, Bentivoglio M. Drug resistance and hippocampal damage after delayed treatment of pilocarpine-induced epilepsy in the rat. Brain Res Bull 2006; 71: 127–138. 22 Dalby NO, Mody I. The process of epileptogenesis: a pathophysiological approach. Curr Opin Neurol 2001; 14: 187–192. 23 Pitk€anen A, Lukasiuk K. Mechanisms of epileptogenesis and potential treatment targets. Lancet Neurol 2011; 10: 173–186. 24 Biagini G, Baldelli E, Longo D, Pradelli L, Zini I, Rogawski MA, Avoli M. Endogenous neurosteroids modulate epileptogenesis in a model of temporal lobe epilepsy. Exp Neurol 2006; 201: 519–524. 25 Biagini G, Longo D, Baldelli E, Zoli M, Rogawski MA, Bertazzoni G, Avoli M. Neurosteroids and epileptogenesis in the pilocarpine model: evidence
Journal of Neuroendocrinology, 2013, 25, 980–990
Neurosteroids and seizures
26 27
28
29
30 31
32
33
34
35
36
37
38
39 40
41 42 43
for a relationship between P450scc induction and length of the latent period. Epilepsia 2009; 50(Suppl. 1): 53–58. Biagini G, Panuccio G, Avoli M. Neurosteroids and epilepsy. Curr Opin Neurol 2010; 23: 170–176. Biagini G, Marinelli C, Panuccio G, Puia G, Avoli M. Glia-neuron interactions: neurosteroids and epileptogenesis. In: Noebels JL, Avoli M, Rogawski M, Olsen R, Delgado-Escueta AV, eds. Jasper’s Basic Mechanisms of the Epilepsies – 4th Edition, Contemporary Neurology Series. 80. New York, NY: Oxford University Press, 2012: 635–647. L€oscher W, Brandt C. Prevention or modification of epileptogenesis after brain insults: experimental approaches and translational research. Pharmacol Rev 2010; 62: 668–700. D’Ambrosio R, Hakimian S, Stewart T, Verley DR, Fender JS, Eastman CL, Sheerin AH, Gupta P, Diaz-Arrastia R, Ojemann J, Miller JW. Functional definition of seizure provides new insight into post-traumatic epileptogenesis. Brain 2009; 132: 2805–2821. Walker MC, White HS, Sander JW. Disease modification in partial epilepsy. Brain 2002; 125: 1937–1950. Raol YH, Lund IV, Bandyopadhyay S, Zhang G, Roberts DS, Wolfe JH, Russek SJ, Brooks-Kayal AR. Enhancing GABAA receptor a1 subunit levels in hippocampal dentate gyrus inhibits epilepsy development in an animal model of temporal lobe epilepsy. J Neurosci 2006; 26: 11342– 11346. Bortel A, Levesque M, Biagini G, Gotman J, Avoli M. Convulsive status epilepticus duration as determinant for epileptogenesis and interictal discharge generation in the rat limbic system. Neurobiol Dis 2010; 40: 478–489. Goffin K, Nissinen J, Van Laere K, Pitk€anen A. Cyclicity of spontaneous recurrent seizures in pilocarpine model of temporal lobe epilepsy in rat. Exp Neurol 2007; 205: 501–505. Jung S, Jones TD, Lugo JN Jr, Sheerin AH, Miller JW, D’Ambrosio R, Anderson AE, Poolos NP. Progressive dendritic HCN channelopathy during epileptogenesis in the rat pilocarpine model of epilepsy. J Neurosci 2007; 27: 13012–13021. Williams PA, White AM, Clark S, Ferraro DJ, Swiercz W, Staley KJ, Dudek FE. Development of spontaneous recurrent seizures after kainateinduced status epilepticus. J Neurosci 2009; 29: 2103–2112. Ben-Ari Y, Dudek FE. Primary and secondary mechanisms of epileptogenesis in the temporal lobe: there is a before and an after. Epilepsy Curr 2010; 10: 118–125. van Vliet EA, Aronica E, Tolner EA, Lopes da Silva FH, Gorter JA. Progression of temporal lobe epilepsy in the rat is associated with immunocytochemical changes in inhibitory interneurons in specific regions of the hippocampal formation. Exp Neurol 2004; 187: 367– 379. Fabene PF, Navarro Mora G, Martinello M, Rossi B, Merigo F, Ottoboni L, Bach S, Angiari S, Benati D, Chakir A, Zanetti L, Schio F, Osculati A, Marzola P, Nicolato E, Homeister JW, Xia L, Lowe JB, McEver RP, Osculati F, Sbarbati A, Butcher EC, Constantin G. A role for leukocyteendothelial adhesion mechanisms in epilepsy. Nat Med 2008; 14: 1377– 1383. Vezzani A, French J, Bartfai T, Baram TZ. The role of inflammation in epilepsy. Nat Rev Neurol 2011; 7: 31–40. Kovacs R, Heinemann U, Steinh€auser C. Mechanisms underlying bloodbrain barrier dysfunction in brain pathology and epileptogenesis: role of astroglia. Epilepsia 2012; 53(Suppl. 6): 53–59. Losi G, Cammarota M, Carmignoto G. The role of astroglia in the epileptic brain. Front Pharmacol 2012; 3: 132. Olah M, Biber K, Vinet J, Boddeke HW. Microglia phenotype diversity. CNS Neurol Disord Drug Targets 2011; 10: 108–118. Vinet J, Weering HR, Heinrich A, K€alin RE, Wegner A, Brouwer N, Heppner FL, Rooijen NV, Boddeke HW, Biber K. Neuroprotective function for
Journal of Neuroendocrinology, 2013, 25, 980–990
44 45
46
47 48
49
50
51
52
53
54
55
56
57
58
59
60
61
989
ramified microglia in hippocampal excitotoxicity. J Neuroinflammation 2012; 9: 27. Fabene PF, Bramanti P, Constantin G. The emerging role for chemokines in epilepsy. J Neuroimmunol 2010; 224: 22–27. Abraham J, Fox PD, Condello C, Bartolini A, Koh S. Minocycline attenuates microglia activation and blocks the long-term epileptogenic effects of early-life seizures. Neurobiol Dis 2012; 46: 425–430. Gandhi R, Laroni A, Weiner HL. Role of the innate immune system in the pathogenesis of multiple sclerosis. J Neuroimmunol 2010; 221: 7– 14. Wee YV. Inflammation in neurological disorders: a help or a hindrance? Neuroscientist 2010; 16: 408–420. Almolda B, Gonzalez B, Castellano B. Activated microglial cells acquire an immature dendritic cell phenotype and may terminate the immune response in an acute model of EAE. J Neuroimmunol 2010; 223: 39–54. Penkowa M, Molinero A, Carrasco J, Hidalgo J. Interleukin-6 deficiency reduces the brain inflammatory response and increases oxidative stress and neurodegeneration after kainic acid-induced seizures. Neuroscience 2001; 102: 805–818. Mirrione MM, Konomos DK, Gravanis I, Dewey SL, Aguzzi A, Heppner FL, Tsirka SE. Microglial ablation and lipopolysaccharide preconditioning affects pilocarpine-induced seizures in mice. Neurobiol Dis 2010; 39: 85–97. Corpechot C, Robel P, Axelson M, Sj€ovall J, Baulieu EE. Characterization and measurement of dehydroepiandrosterone sulfate in rat brain. Proc Natl Acad Sci USA 1981; 78: 4704–4707. Le Goascogne C, Robel P, Gouezou M, Sananes N, Baulieu EE, Waterman M. Neurosteroids: cytochrome P-450scc in rat brain. Science 1987; 237: 1212–1215. Ukena K, Usui M, Kohchi C, Tsutsui K. Cytochrome P450 side-chain cleavage enzyme in the cerebellar Purkinje neuron and its neonatal change in rats. Endocrinology 1998; 139: 137–147. Shibuya K, Takata N, Hojo Y, Furukawa A, Yasumatsu N, Kimoto T, Enami T, Suzuki K, Tanabe N, Ishii H, Mukai H, Takahashi T, Hattori TA, Kawato S. Hippocampal cytochrome P450s synthesize brain neurosteroids which are paracrine neuromodulators of synaptic signal transduction. Biochim Biophys Acta 2003; 1619: 301–316. Zwain IH, Yen SS. Neurosteroidogenesis in astrocytes, oligodendrocytes, and neurons of cerebral cortex of rat brain. Endocrinology 1999; 140: 3843–3852. Stephenson DT, Schober DA, Smalstig EB, Mincy RE, Gehlert DR, Clemens JA. Peripheral benzodiazepine receptors are colocalized with activated microglia following transient global forebrain ischemia in the rat. J Neurosci 1995; 15: 5263–5274. Banati RB, Myers R, Kreutzberg GW. PK (‘peripheral benzodiazepine’)binding sites in the CNS indicate early and discrete brain lesions: microautoradiographic detection of [3H]PK11195 binding to activated microglia. J Neurocytol 1997; 26: 77–82. Kuhlmann AC, Guilarte TR. Cellular and subcellular localization of peripheral benzodiazepine receptors after trimethyltin neurotoxicity. J Neurochem 2000; 74: 1694–1704. Rao VL, Bowen KK, Rao AM, Dempsey RJ. Up-regulation of the peripheral-type benzodiazepine receptor expression and [3H]PK11195 binding in gerbil hippocampus after transient forebrain ischemia. J Neurosci Res 2001; 64: 493–500. Furukawa A, Miyatake A, Ohnishi T, Ichikawa Y. Steroidogenic acute regulatory protein (StAR) transcripts constitutively expressed in the adult rat central nervous system: colocalization of StAR, cytochrome P-450SCC (CYP XIA1), and 3bhydroxysteroid dehydrogenase in the rat brain. J Neurochem 1998; 71: 2231–2238. Sierra A. Neurosteroids: the StAR protein in the brain. J Neuroendocrinol 2004; 16: 787–793.
© 2013 British Society for Neuroendocrinology
990
G. Biagini et al.
62 Papadopoulos V, Baraldi M, Guilarte TR, Knudsen TB, Lacapere JJ, Lindemann P, Norenberg MD, Nutt D, Weizman A, Zhang MR, Gavish M. Translocator protein (18 kDa): new nomenclature for the peripheral-type benzodiazepine receptor based on its structure and molecular function. Trends Pharmacol Sci 2006; 27: 402–409. 63 Biagini G, Baldelli E, Longo D, Contri MB, Guerrini U, Sironi L, Gelosa P, Zini I, Ragsdale DS, Avoli M. Proepileptic influence of a focal vascular lesion affecting entorhinal cortex-CA3 connections after status epilepticus. J Neuropathol Exp Neurol 2008; 67: 687–701. 64 Racine RJ. Modification of seizure activity by electrical stimulation: II. Motor seizure. Electroencephalogr Clin Neurophysiol 1972; 32: 281–294. 65 Belelli D, Lambert JJ. Neurosteroids: endogenous regulators of the GABAA receptor. Nat Rev Neurosci 2005; 6: 565–575. 66 Mukai Y, Higashi T, Nagura Y, Shimada K. Studies on neurosteroids XXV. Influence of a 5a-reductase inhibitor, finasteride, on rat brain neurosteroid levels and metabolism. Biol Pharm Bull 2008; 31: 1646–1650. 67 Concas A, Mostallino MC, Porcu P, Follesa P, Barbaccia ML, Trabucchi M, Purdy RH, Grisenti P, Biggio G. Role of brain allopregnanolone in the plasticity of c-aminobutyric acid type A receptor in rat brain during pregnancy and after delivery. Proc Natl Acad Sci USA 1998; 95: 13284– 13289. 68 Rustichelli C, Pinetti D, Lucchi C, Ravazzini F, Puia G. Simultaneous determination of pregnenolone sulphate, dehydroepiandrosterone and allopregnanolone in rat brain areas by liquid chromatography-electrospray tandem mass spectrometry. J Chromatogr B 2013; 930: 62–69. 69 Reddy DS. Neuroendocrine aspects of catamenial epilepsy. Horm Behav 2013; 63: 254–266. 70 Maguire JL, Stell BM, Rafizadeh M, Mody I. Ovarian cycle-linked changes in GABAA receptors mediating tonic inhibition alter seizure susceptibility and anxiety. Nat Neurosci 2005; 8: 797–804. 71 Guille C, Spencer S, Cavus I, Epperson CN. The role of sex steroids in catamenial epilepsy and premenstrual dysphoric disorder: implications for diagnosis and treatment. Epilepsy Behav 2008; 13: 12–24. 72 Smith SS. Withdrawal properties of a neuroactive steroid: implications for GABAA receptor gene regulation in the brain and anxiety behavior. Steroids 2002; 67: 519–528. 73 B€ackstr€om T, Andersson A, Andree L, Birzniece V, Bixo M, Bj€orn I, Haage D, Isaksson M, Johansson IM, Lindblad C, Lundgren P, Nyberg
© 2013 British Society for Neuroendocrinology
74 75
76
77
78 79 80 81 82
83 84 85 86 87
S, Odmark IS, Str€omberg J, Sundstr€om-Poromaa I, Turkmen S, Wahlstr€om G, Wang M, Wihlb€ack AC, Zhu D, Zingmark E. Pathogenesis of menstrual cycle-linked CNS disorders. Ann NY Acad Sci 2003; 1007: 42–53. Selye H. On the hormonal activity of a steroid compound. Science 1941; 94: 94. Reddy DS, Castaneda DC, O’Malley BW, Rogawski MA. Anticonvulsant activity of progesterone and neurosteroids in progesterone receptor knockout mice. J Pharmacol Exp Ther 2004; 310: 230–239. Kokate TG, Banks MK, Magee T, Yamaguchi S, Rogawski MA. Finasteride, a 5a-reductase inhibitor, blocks the anticonvulsant activity of progesterone in mice. J Pharmacol Exp Ther 1999; 288: 679– 684. Frye CA, Rhodes ME, Walf A, Harney J. Progesterone reduces pentylenetetrazol-induced ictal activity of wild type mice but not those deficient in type I 5a-reductase. Epilepsia 2002; 43(Suppl. 5): 14–17. Herzog AG. Hormonal therapies: progesterone. Neurotherapeutics 2009; 6: 383–391. Reddy DS, Kim HY, Rogawski MA. Neurosteroid withdrawal model of perimenstrual catamenial epilepsy. Epilepsia 2001; 42: 328–336. Reddy DS, Rogawski MA. Neurosteroid replacement therapy for catamenial epilepsy. Neurotherapeutics 2009; 6: 392–401. Reddy DS. The role of neurosteroids in the pathophysiology and treatment of catamenial epilepsy. Epilepsy Res 2009; 85: 1–30. Lawrence C, Martin BS, Sun C, Williamson J, Kapur J. Endogenous neurosteroid synthesis modulates seizure frequency. Ann Neurol 2010; 67: 689–693. Taubøll E, Lundervold A, Gjerstad L. Temporal distribution of seizures in epilepsy. Epilepsy Res 1991; 8: 153–165. Herzog AG. Progesterone therapy in women with complex partial and secondary generalized seizures. Neurology 1995; 45: 1660–1662. Herzog AG, Frye CA. Seizure exacerbation associated with inhibition of progesterone metabolism. Ann Neurol 2003; 53: 390–391. Mani SK, Oyola MG. Progesterone signaling mechanisms in brain and behavior. Front Endocrinol 2012; 3: 7. Pugnaghi M, Monti G, Biagini G, Meletti S. Temporal lobe epilepsy exacerbation during pharmacological inhibition of endogenous neurosteroid synthesis. BMJ Case Rep 2013; pii: bcr2012008204.
Journal of Neuroendocrinology, 2013, 25, 980–990
