GLUTAMATE AS THE NEUROTRANSMITTER OF CEREBELLAR GRANULE CELLS IN THE RAT: ELECTROPHYSIOLOGICAL EVIDENCE

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Abstract
1 Glutamate and the excitatory aminoacid antagonist, α-aminoadipic acid (αAA), have been applied by microiontophoresis to Purkinje cells in the rat cerebellum. 2 Glutamate produced excitation of Purkinje cells and αAA selectively reduced that excitation without affecting responses to acetylcholine or hydrogen ions. 3 Monosynaptic spikes were evoked in Purkinje cells by stimulating the parallel fibres. αAA had little effect on these spikes when applied alone. 4 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. 5 These results support neurochemical evidence that glutamic acid may be the neurotransmitter released by granule cell parallel fibres.