Cooperating Synapses

Abstract

In parts of the brain, such as the hippocampus, synapses are densely packed and activation of a single synapse may influence the activity of adjacent neurons, the presynaptic neuron, as well as the postsynaptic target neuron. The phenomenon by which adjacent synapses are activated, called synaptic cooperation by Arnth-Jensen et al. , has important implications, because drugs may alter this cooperative response, and this response may be an important component to the induction of long-term potentiation. Arnth-Jensen et al. used hippocampal slices and the glutamate transport inhibitor TBOA to show that when glutamate uptake was blocked, the duration of excitatory postsynaptic currents (EPSCs) was prolonged. In an experiment designed to measure charge transfer as a result of activation of N -methyl-D-aspartate (NMDA) receptor activation, they showed that extrasynaptic receptors were activated even when the glutamate uptake was fully functional. In addition to controlling the spatial activation of glutamate receptors, glutamate uptake influenced the duration of the response at a single synaptic pair under conditions of high-frequency stimulation. The implications of these results and the functional relevance of neurotransmitter spillover are discussed by Diamond. N. Arnth-Jensen, D. Jabaudon, M. Scanziani, Cooperation between independent hippocampal synapses is controlled by glutamate uptake. Nature Neurosci. 5 , 325-331 (2002). [Online Journal] J. S. Diamond, A broad view of glutamate spillover. Nature Neurosci. 5 , 291-292 (2002). [Online Journal]