GABAPENTIN INCREASES GABA-INDUCED DEPOLARIZATION IN RAT NEONATAL OPTIC-NERVE

Membrane potential changes of rat neonatal optic nerves were studied i n a sucrose-gap chamber. Nipecotic acid (NPA), which blocks uptake and promotes release of GABA, resulted in a bicuculline-sensitive depolar ization (3.08 +/- 0.3 mV, n = 5). Pretreatment of the nerves with the anticonvulsant gabapentin (100 muM for 1 h) resulted in a near doublin g of the NPA-induced depolarization (6.64 +/- 0.54 mV, n = 5). Gabapen tin itself did not alter membrane potential, nor did brief application s of gabapentin enhance the NPA- or GABA-induced depolarization. Thus, gabapentin appears to enhance the releasable pool of GABA in this CNS neural system. These results have implications for the mechanism of t he anticonvulsant properties of gabapentin.