Synaptic activation of AMPA receptors inhibits GABA release from cerebellar interneurons

A single neurotransmitter elicits diverse physiological responses through a ctivation of multiple receptor subtypes and/or heterosynaptic interactions involving distinct synaptic targets. We found that a typical excitatory tra nsmitter released from the climbing fiber (CF) in the cerebellar cortex not only excited Purkinje cells directly but also presynaptically inhibited GA BAergic transmission from interneurons converging on the same Purkinje cell s. Both homosynaptic and heterosynaptic actions of the CF transmitter (poss ibly glutamate) were mediated by activation of AMPA receptors. Dual AMPA re ceptor-mediated functions of excitation and disinhibition may ensure transm ission of cerebellar CF signals controlling sensorimotor coordination.