A POSTSYNAPTIC EXCITATORY AMINO-ACID TRANSPORTER WITH CHLORIDE CONDUCTANCE FUNCTIONALLY REGULATED BY NEURONAL-ACTIVITY IN CEREBELLAR PURKINJE-CELLS

Excitatory amino acid (EAA) neurotransmitters induce postsynaptic depo larization by activating receptor-mediated cation conductances, a proc ess known to underlie changes in synaptic efficacy. Using a patch-clam p method, we demonstrate here an EAA-dependent postsynaptic anion cond uctance mediated by EAA transporters present on cerebellar Purkinje ce ll bodies and dendrites in culture. This transporter-mediated current was modulated by neuronal activity: it exhibited facilitation for >20 min after transient depolarization accompanied by Ca2+ influx. Evidenc e is presented suggesting that the transporter facilitation is mediate d by arachidonate release after Ca2+-dependent activation of phospholi pase A(2), which exists in Purkinje cells. This postsynaptic reuptake system may represent a novel modulatory mechanism of synaptic transmis sion as well as prevent neuronal excitotoxicity.