Gabapentin increases GABA-induced depolarization in rat neonatal optic nerve.

Membrane potential changes of rat neonatal optic nerves were studied in a sucrose-gap chamber. Nipecotic acid (NPA), which blocks uptake and promotes release of GABA, resulted in a bicuculline-sensitive depolarization (3.08 +/- 0.3 mV, n = 5). Pretreatment of the nerves with the anticonvulsant gabapentin (100 microM for 1 h) resulted in a near doubling of the NPA-induced depolarization (6.64 +/- 0.54 mV, n = 5). Gabapentin itself did not alter membrane potential, nor did brief applications 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 the anticonvulsant properties of gabapentin.