EFFECT OF KHAYA SENEGALENSIS ON CAT BLOOD PRESSURE AND GROSS LOCOMOTION IN CHICKS *T.O. Olurishe, J.A. Anuka and S. Nnanta, Department of Pharmacology and Clinical Pharmacy, Ahmadu Bello University, PMB 1045 Zaria, Nigeria
*Author for Correspondence Department of Pharmacology & Clin. Pharm. A.B.U. PMB 1045, Zaria, Nigeria E-mail address:
[email protected];
[email protected] (Olurishe, T.O). Phone: 08036005775; 08053668228
ABSTRACT The objective of the present study was to evaluate the effect of the methanolic root bark extract of Khaya senegalensis (Meliaceae) on blood pressure using the anaesthetized cat model as well as its effect on gross locomotor activity in two-day old chicks. The results showed that at dose levels between 1.8 and 15 mg/kg the extract produced a non-dose dependent decrease in blood pressure in the cat blood pressure model while causing a significant reduction in gross locomotor activity in the chicks. It also produced sedation and sleep in the chicks at 5, 10 and 15 mg/kg. These results suggest that the extract may posses some activities that may be useful in blood pressure reduction as well as in sedation and hypnosis. Keywords: Khaya senegalensis, Cat blood pressure, gross locomotor activity, chicks
2
Introduction Much of the developing world still relies on plant and non orthodox methods for the treatment of ailments. Resource inequality is also consistently found within developing countries, especially in terms of health service facilities (Navarro, 1974). With about 80% of the population in developing countries living in the rural areas (Farnsworth and Soejarto, 1985) where access to western medicine is largely unavailable or overstretched, traditional medical practice remains the source of Medicare to the rural dwellers. This is not entirely surprising as approximately 119 pure chemical substances extracted from higher plants are used in medicine throughout the world (Farnsworth and Soejarto, 1985). Khaya senegalensis is a tall plant spanning over 30 meters and is found in various parts of Africa such as Guinea, Senegal, Ivory Coast, Guinea Bissau, Egypt and the northern parts of Nigeria (Dalziel, 1955). It has been reportedly used in the treatment of menstrual pain, fever, and stomach ache. It has been reportedly used also in the treatment of external ulcers and malaria fever (Olayinka et al., 1992). In Senegal it is used for skin infections and blennorhagia (Le Grand, 1989). In Ivory Coast, it is also used as an abortificient. Research has shown the HIV-1 protease inhibition by the Khaya leaves obtained from Sudan (Hussein et al., 1999). Biological screening of drugs has been found to yield previously unreported activities. Serendipity has also played a great role in the development of some of the most widely used drugs today. In this study the effect of the methanolic crude extract of the root bark is evaluated on two in vivo models to investigate the activity of the extract on cat blood pressure as well as its effect on gross locomotor behavior in two day old chicks.
3
Methods and Materials (a)
Collection and Preparation of Crude drug
The root bark material was obtained by digging manually into the ground in the month of January in Zaria, Kaduna State, Nigeria. The plant material was identified in the Herbarium of the Biological Sciences Department of the Ahmadu Bello University, Zaria where a Herbarium Specimen with Voucher Number 900181 is deposited. The root bark was carefully cleaned to rid it off any adulterants and dried for about two weeks under laboratory condition away from sunlight to avoid photolyis and possible denaturation of any phytochemical constituents present. The dried plant material was then size reduced to fine powder using a grinder and subsequently subjected to twenty four hour maceration in cold methanol solution. After the maceration, the resulting macerate was evaporated to dryness under a thermostatically regulated temperature of 60°C. The resultant crude drug was carefully dried and stored in a dessicator for subsequent uses in the experiments. (b)
Cat Blood Pressure Experiment
The cat blood pressure experiment was carried out using cats obtained from the animal house of the Department of Pharmacology and Clinical Pharmacy, Ahmadu Bello University, Zaria. The three cats used were within the weight range of 2.5-2.8 kg and were subjected to a twenty-four hour acclimatization period in the laboratory. The cat was anaesthetized with an i.p. injection of pentobarbitone (40 mg/kg). This was then followed by careful cannulation of the femoral vein through which drugs were administered. Before the cannulation, heparin was administered to the animal to prevent blood clotting. The blood pressure of the animal was then recorded by an Ugo Basil Recording microdynamometer (Model 7050) through the cannulated carotid artery, which was connected to a transducer. The speed at which the microdynamometer was set was 24 mm/minute. Increasing doses of the extract were administered to the cat after which the extract was interacted with adrenaline.
4
(c)
Gross Locomotor Experiment
Twenty-five two day old chicks were obtained from the National Animal Production Research Institute, Zaria. The animals were placed in a multi compartmental cage with each compartment being a 6 inch square. The animals had been previously weighed and each group consisted of four chicks. Four groups of chicks were used for the study with one group on normal saline and the other groups receiving 5, 10 and 15 mg/kg of the extract all administered via the intraperitoneal route. The experiment was performed in a quiet laboratory over a cumulative four hour duration for each chick. The chicks were scored for different behaviors such as pecking, jumping, running, sedation, hypnosis and vocalization. Chicks were regarded as being sedated or depressed when they were quiet and immobile with or without closure of the eyes for over five minutes and with or without drooping of their heads. They were regarded as being asleep when both eyes were closed; the chicks were either crouching with their beaks on the floor or standing with head leaning against the wall of the cage (Fungner and Hoefke, 1971).
Results Figures 1 shows the effect of graded doses of the extract on cat blood pressure while Figure 2 shows the effect of the extract on blood pressure in the presence of adrenaline. Figures 3 and 4 depict the effect of various doses of the extract on gross locomotor activity and sedation
5
250
Saline
5mg/kg
10mg/kg
15mg/kg
Activity Count
200
150
100
50
0 1
2
3
4
Time (Hours)
Figure 3: Effect of Khaya senegalensis on gross locomotion in 2-day chicks
6
250
5mg/kg 10mg/kg 15mg/kg
Duration (Minutes)
200
150
100
50
0 Sedation
Sleep
Figure 4:Sedative-hypnotic effects of Khaya senegalensis
7
Discussion Figure 1 shows the effect of the extract on the anesthetized cat. The extract within the dose levels tested in the study produced a non dose dependent decrease in the cat blood pressure. This decrease was however transient as the blood pressure soon afterwards returned to normal. The reduction in blood pressure cannot be directly attributed to the inhibition of adrenergic receptors on the heart or blood vessels in which case bradycadia or vasodilation will be expected to be the mechanism of blood pressure reduction. This is because the effect of adrenaline on the cat blood pressure was neither adversely affected nor antagonized when the extract was administered before or after the injection of adrenaline to the cat (Figure 2). The failure of the extract to abolish the effect of adrenaline may suggest that the blood pressure reduction may be by some indirect or unknown mechanisms other than those of adrenergic receptor antagonism. However, it is unclear whether higher doses may give results to the contrary. The extract at doses of 5, 10 and 15 mg/kg produced a dose dependent reduction in gross locomotor activity in two day old chicks, when compared to the negative control group on normal saline (Figure 3). This results shows that the extract may contain substances or constituents that may have central nervous system depressant effects or active principles that may be useful in the management of anxiety or insomnia. This is evidenced by the sedation and sleep that was also produced by the extract. This was also a dose dependent effect (Figure 4). The chicks that received 10 and 15 mg/kg of the extract were sedated and also slept particularly in the third and fourth hours of the experiment. The exact mechanism of the sedation and sleep is not known at the moment. However it may not be unconnected with the potentiation of the neural inhibition of gamma amino butyric acid (GABA) pathway which is involved in wakefulness and sedation (Harvey, 1985). It may also act in a manner similar to diazepam, which acts chiefly on the brain reticular activating system, the median forebrain
8
bundle and the hypothalamus to produce its anxiolytic and hypnotic effects (Laurence et al., 1999). Conclusion The results of this study show clearly that Khaya senegalensis posseses some blood pressure reducing properties which may be harnessed into an antihypertensive agent while it also shows potential as being a useful tool in the management of anxiety and treatment of insomnia.
Recommendation Further investigations are on going to elucidate the mechanisms for the pharmacological potentials seen in the current study.
Acknowledgement The authors wish to acknowledge the assistance of Mr. J. Kono and Mallam I. Adamu of the Department of Pharmacology and Clinical Pharmacy, A.B.U. Zaria
References Dalziel, J.M. (1955). The Useful Plants of West Tropical Africa. Watmoughs Limited Idle, Bradford. P.323-326 Farnsworth, N.R. and Soejarto, D.D. (1985). Potential Consequences of Plant Extinction in the United States on the Current and Future Availability of Prescription Drugs. Econ. Bot. 39 (3): 231-240. Fungner, A and Hoefke, W (1971). A sleep-like state in chicks caused by biogenic amines and other compounds; quantitative evaluation. Arzneimitted/forsch. 21:1243-1252
9
Hussein, G; Miyashiro, H; Nakamura N.; Kawahata T.; Otake, T. and Shimotohno, K. (1999). Inhibitory effects of Sudanese plant extracts on HIV-1 protease. Phytother. Res. 13 (1): 31-39 Harvey, S.C. (1985). Hypnotics and Sedatives In: Gilman, A.G. and Goodman, L.S. (eds.) Goodman and Gilman’s, The Pharmacological Basis of Therapeutics 7th Edition. Macmillan Publishers New York pp 339-346 Laurence, D.R., Bennett, P.N. and Brown, M.J. (ed.) (1999). Clinical Pharmacology. Churchill Livingstone, London. Pp.317-326 Le Grand, A. (1989). Anti-Infectious Phytotherapy of the Tree-Savannah, Senegal (Western Africa) III: A Review of the Phytochemical Substances and AntiMicrobial Activity of 43 Species. J. Ethno. 25 (3): 315-338. Navarro, V. (1974). "The Underdevelopment of health or the health of Underdevelopment: An Analysis of the Distribution of Human Health Resources in Latin America." Intern. J. Health Serv. 4: 5-27. Olayinka, A.O., Onoruvwe, O. and Lot, T.Y. (1992). Cardiovascular Effects in Rodents of the Methanolic Extract of the Stem Bark of Khaya senegalensis A. Juss. Phytother. Res. 6 (5): 282-284.
10
