PBIO SEMINAR SERIES

Neuronal glutamate transporters shape synaptic signaling and plasticity in the hippocampus

Wednesday - April 09, 2008
07-08 SEMINAR SERIES
CHDD, room 150

Jeff Diamond
Senior Investigator - Synaptic Physiology Unit NIH / NINDS
Speaker's website

Host: Andres Barria

We study the dynamics of synaptic transmission in the hippocampus and the retina. We want to understand which features of synapses affect their strength, reliability and, ultimately, their function within neural circuits. In the hippocampus, we ask how synaptic transmission depends upon the diffusion dynamics of glutamate, and how glutamate transporters regulate this process. In many cases, synaptically released glutamate can diffuse beyond the cleft to activate targets outside the synapse, a phenomenon referred to as "spillover." We do not yet understand the impact of spillover on information processing in the brain. The extent to which spillover occurs depends on how long glutamate is permitted to diffuse following its synaptic release. We measure this by recording electrophysiological signals associated with glutamate uptake into glial cells in brain slices. In addition, we record the time course of synaptic and extrasynaptic receptor activation using similar recordings from neurons. We have found that glial transporters remove synaptically released glutamate very quickly - within a millisecond following its release, but that receptors are still activated by spillover. Further experiments show that neuronal transporters limit the activation of perisynaptic NMDA receptors in an activity-dependent fashion and therefore may regulate the induction of certain forms of synaptic plasticity.