Effects of gamma-aminobutyric acid on nerve terminal excitability in a slice preparation of cuneate nucleus.

1 Superfusion of a slice preparation of the rat cuneate nucleus with gamma-aminobutyric acid (GABA) depolarized the afferent nerve fibres and increased their excitability. However, before the depolarization had reached its peak the increased excitability reversed to a decreased excitability, an effect which outlasted the depolarization. 2 Both components of the GABA excitability response were dose-related Cl--dependent and antagonized by bicuculline. 3 Possible mechanisms underlying the sequence of excitability changes are discussed.