SHORT-TERM AND LONG-TERM SYNAPTIC DEPRESSION IN RAT NEOSTRIATUM

1. We have examined plasticity at glutamatergic synapses on neurons in slices of neostriatum, a forebrain area involved in movement and cogn itive function. 2. High-frequency stimulation of afferent inputs to ne ostriatal neurons induced depression of glutamatergic synaptic transmi ssion. Depression could be induced using either prolonged trains or sh ort repetitive bursts of high-frequency stimulation. Depression develo ped within seconds after such stimulation. Responses recovered to base line levels within 10 min in most slices but persisted for up to 60 mi n in others. 3. Postsynaptic passive electrical properties and the abi lity to elicit action potentials by postsynaptic depolarization were n ot altered during depression.4. The magnitude and time course of depre ssion was similar whether postsynaptic responses were mediated by alph a amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) or N-meth yl-D-aspartate (NMDA) type glutamate receptors. Depression was not alt ered by antagonism of AMPA or NMDA receptors or potentiation of AMPA r eceptor function with aniracetam. 5. Depression was blocked by treatme nts that increase transmitter release including increased extracellula r Ca2+, application of 4-aminopyridine, or application of phorbol este r. 6. Our findings indicate that glutamatergic synapses in neostriatum are capable of expressing a form of synaptic depression that may invo lve decreased glutamate release.