Synaptic Transmission

OK, Everyone Keep Quiet

Science's STKE  07 Nov 2006:
Vol. 2006, Issue 360, pp. tw378
DOI: 10.1126/stke.3602006tw378

Glutamate transporters in glial cells and postsynaptic neurons are believed to accumulate synaptically released glutamate; however, the role of presynaptic glutamate transporters has been unclear (see Wadiche and von Gersdorff). Veruki et al. combined electrophysiological and pharmacological analysis to investigate the role of presynaptic glutamate transporters that mediate a prominent anion current uncoupled from glutamate uptake in retinal rod bipolar (RB) cells. After showing that glutamate transporter-mediated inward currents recorded from RB cells in rat retinal slices were largest and fastest when elicited by puffs of glutamate delivered near axon terminals in the inner plexiform layer, the authors confirmed the presynaptic location of the transporters by recording from isolated patches. Dual recordings from RB cells and synaptically connected AII amacrine cells, as well as a comparison of the time course of transporter currents recorded in RB cells in response to released glutamate to currents recorded from patches, indicated that transporters on RB cells were located perisynaptically (and farther from the site of release than were the postsynaptic receptors). Moreover, transporter currents in RB cells were activated not only by auto-released glutamate but also by glutamate released from neighboring RB cells. Transporter activation led to a decrease in transmitter release and thus a reduction in the postsynaptic response. Thus, presynaptic RB glutamate transporters appear to mediate both auto- and lateral inhibition of transmitter release.

M. L. Veruki, S. H. Mørkve, E. Hartveit, Activation of a presynaptic glutamate transporter regulates synaptic transmission through electrical signaling. Nat. Neurosci. 9, 1388-1396 (2006). [PubMed]

J. I. Wadiche, H. von Gersdorff, Long-distance signaling via presynaptic glutamate transporters. Nat. Neurosci. 9, 1352-1353 (2006). [PubMed]