Fast removal of synaptic glutamate by postsynaptic transporters

Glutamate transporters are believed to remove glutamate from the synaptic c left only slowly because they cycle slowly. However, we show that when glut amate binds to postsynaptic transporters at the cerebellar climbing fiber s ynapse, it evokes a conformation change and inward current that reflect glu tamate removal from the synaptic cleft within a few milliseconds, a time sc ale much faster than the overall cycle time. Contrary to present models, gl utamate removal does not require binding of an extracellular proton, and th e time course of transporter anion conductance activation differs from that of glutamate removal. The charge movement associated with glutamate remova l is consistent with the majority of synaptically released glutamate being removed from the synaptic cleft by postsynaptic transporters.