Hyperpolarizing action of baclofen on neurons in the rat substantia nigra slice.

GABA, muscimol and L-baclofen inhibited zona compacta neurons in the rat substantia nigra slice, D-baclofen was inactive, L-baclofen produced a potent hyperpolarization of the membrane potential. The actions of muscimol but not GABA and L-baclofen were reversed by bicuculline. The actions of muscimol and baclofen are likely to be mediated by interactions with two different receptors.