Presynaptic actions of gamma-aminobutyric acid and some antagonists in a slice preparation of cuneate nucleus.

1 A slice preparation of the rat cuneate nucleus is described which is suitable for electrophysiological studies on the presynaptic action of drugs. 2. Superfusion of a slice with gamma-aminobutyric acid (GABA) depolarized the afferent nerves in a concentration-related manner. The responses were Cl-dependent. Depolarizations to high concentrations of GABA often faded. Glycine and L-glutamate had little effect. 3 (+)-Bicuculline antagonized GABA in an apparently competitive manner (pA2 = 5.35) at low response levels. Strychnine was 10 times less potent. Responses to high concentrations of GABA were sometimes potentiated by (+)-bicuculline and strychnine. 4 Bemegride and leptazol both antagonized GABA, but with low potency and in a manner which was clearly not competitive.