Excitatory and inhibitory responses of Purkinje cells, in the rat cerebellum in vivo, induced by excitatory amino acids.

Responses of rat cerebellar Purkinje cells to iontophoretically administered excitatory amino acids have been studied in vivo. Responses to N-methyl-D-aspartate (NMDA) were either biphasic (excitation followed by inhibition) or purely inhibitory and were antagonized by the selective NMDA-receptor antagonist, 2-amino-5-phosphonovalerate. Quisqualate and kainate either excited or induced biphasic responses, in these neurones, which were only reduced by amino acid antagonists that acted at non-NMDA receptors. The excitatory amino acid-induced inhibitions were also antagonized by the selective gamma-aminobutyric acid (GABA) antagonist, picrotoxin, suggesting that they were indirectly mediated via GABAergic inhibitory interneurones, which could be excited via NMDA and non-NMDA receptors.