REDUCTION OF GABA INHIBITION IN PURKINJE AND CEREBELLAR NUCLEI NEURONS IN CLIMBING FIBER DEAFFERENTED CEREBELLA OF RAT

GABA agonists were iontophoretically applied to Purkinje cells (PCs) o f the cerebellar cortex and to neurons of the cerebellar nuclei (NCNs) in normal and in climbing fibre (CF) deafferented cerebella of rat. T he experiments were performed one and three months after CF deafferent ation obtained by total inferior olive destruction with 3-acetylpyridi ne. All control PCs were dose-dependently inhibited by GABA and muscim ol and nearly all by baclofen. After CF deafferentation, the number of PCs sensitive to muscimol remained the same but the number sensitive to baclofen was greatly reduced one month later and almost absent afte r three months. The number of NCNs inhibited by GABA was slightly redu ced one month after deafferentation compared to controls, but reduced to less than half three months after. Thus CF deafferentation of the P C leads to changes in postsynaptic sensitivity to GABA, the presumed i nhibitory neurotransmitter, affecting GABA(A) receptors of the NCNs an d GABA(B) receptors of the PCs.