GLUTAMATE AS THE NEUROTRANSMITTER OF CEREBELLAR GRANULE CELLS IN THE RAT - ELECTRO-PHYSIOLOGICAL EVIDENCE

Glutamate and the excitatory aminoacid antagonist, α‐aminoadipic acid (αAA), have been applied by microiontophoresis to Purkinje cells in the rat cerebellum. Glutamate produced excitation of Purkinje cells and αAA selectively reduced that excitation without affecting responses to acetylcholine or hydrogen ions. Monosynaptic spikes were evoked in Purkinje cells by stimulating the parallel fibres. αAA had little effect on these spikes when applied alone. When the Purkinje cell excitability was reduced by the iontophoresis of γ‐aminobutyric acid, αAA then produced failure of the monosynaptic spike on 10 of 13 Purkinje cells, in doses shown to be selectively antagonistic towards aminoacids. These results support neurochemical evidence that glutamic acid may be the neurotransmitter released by granule cell parallel fibres. 1979 British Pharmacological Society