How do Gabapentinoids Work?

How do Gabapentinoids Work? James. E. BIGGS, Patrick STEMKOWSKI, Yischen CHEN, Aquilino Lantero GARCIA1 Sascha R.A. ALLES and Peter. A. SMITH Centre for Neuroscience, Univ. of Alberta, Edmonton, AB, Canada, 1 Dpto. de Fisiología y Farmacología, Universidad de Cantabria, Santander, Spain

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Sensory Neuron Cell Body in DRG

Ca2+ channel a2d subunit

Sensory Neuron Cell Body in DRG

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Primary Afferent Terminal in Dorsal Horn

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Control 10mM PGB 5 days

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P 24h) and in the clinic ( ~ 5 days). We therefore studied Ca2+ channel currents in dorsal root ganglion (DRG) neurons and neurotransmitter release in spinal cord by whole-cell recording and confocal Fluo 4 Ca2+ imaging. (Fig 1C). Rat DRG neurons in defined medium culture or spinal neurons in organotypic culture (Fig 1D) were exposed to pregabalin (PGB,10mM) for 5-6 days. We found that PGB reduced Ca2+ channel currents in primary afferent neurons and it decreased transmitter release in the spinal dorsal horn. Data presented below suggest that PGB’s ability to suppress expression of Ca2+ channels may account for its ability to reduce neurotransmitter release.

Peak Amplitude of Ca2+ Response Arbitary Units (au)

The gabapentinoids, pregabalin and gabapentin are frequently used in the management of neuropathic pain. Mechanistically, they are transported into neurons via the system L neutral aminoacid transporter. Once inside, they bind to the a2d subunit of voltage-gated Ca2+ channels. Since these subunits are thought to be involved in the trafficking of channels to nerve terminals and cell bodies, interaction of gabapentinoids with a2d subunit is thought to limit their insertion into cell membranes. Limited expression of functional Ca2+ channels at nerve terminals would be expected to reduce neurotransmitter release but this hypothesis has never directly been tested (Fig 1A and B).

Fig 3. We assessed general dorsal horn excitability by monitoring changes in intracellular Ca2+ produced by stimulation of the dorsal root entry zone. Typical recordings from 3 neurons are shown in A. 5-6 days exposure to 10mM pregabalin reduced the amplitude (B) and area under curve (C) of Ca2+ responses. This effect was blocked by . 2-(-)-endoamino-bicyclo-heptane-2-carboxylic acid (BCH 300mM), an inhibitor of the neutral aminoacid transporter, showing that entry of pregabalin into neurons is required for its action.

Fluo 4 Flourescence Arbitary Units

Introduction and Methods

Fluo 4 Flourescence Arbitary Units

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Acknowledgements

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We thank Naren Ganesan for data presented in Fig 6 and Dr. Klaus Ballanyi for use of confocal microscope and imaging facilities.. Supported by Pfizer Neuropathic Pain Awards Program