PROLONGED PRESENCE OF GLUTAMATE DURING EXCITATORY SYNAPTIC TRANSMISSION TO CEREBELLAR PURKINJE-CELLS

In the molecular layer of the cerebellar cortex, Purkinje cells and in terneurons receive a common excitatory input from parallel fibers. The AMPA/kainate receptor-mediated parallel fiber excitatory postsynaptic current (EPSC) recorded in Purkinje cells decays much more slowly tha n that recorded in interneurons. We show that this slowness of decay d oes not result from dendritic filtering and that it is unlikely to ref lect the deactivation kinetics of the postsynaptic receptors. Agents b locking glutamate uptake prolong the EPSC in Purkinje cells. We conclu de that the slow EPSC decay results from the continued presence of tra nsmitter glutamate. This may be due to retarded transmitter diffusion around spines or to cross-talk between neighboring active synapses.