Glycine Binding Sites of Presynaptic NMDA Receptors May Tonically Regulate Glutamate Release in the Rat Visual Cortex.
In the CNS, activation of N-methyl-d-aspartate receptor ( NMDA-R) glycine binding sites is a prerequisite for activation of postsynaptic NMDA-Rs by the excitatory neurotransmitter glutamate. Here we provide electrophysiological evidence that the glycine binding sites of presynaptic NMDA-Rs regulate glutamate release in layer II/III pyramidal neurons of the rat visual cortex. Specifically, our results reveal that the frequency of miniature excitatory postsynaptic currents is significantly reduced by 7-chloro-kynurenic acid (7-Cl KYNA), a NMDA-R glycine binding site antagonist, and glycine or d-serine reverses this effect. Similar results are obtained when the open-channel NMDA receptor blocker, MK-801, is included in the recording pipette. Our data indicate that the glycine binding site of postsynaptic NMDA-Rs is not saturated. Moreover, they suggest that presynaptic NMDA-Rs are located in layer II/III pyramidal neurons of the rat visual cortex and that the glycine binding site of presynaptic NMDA-Rs tonically regulates glutamate release.[1]References
- Glycine Binding Sites of Presynaptic NMDA Receptors May Tonically Regulate Glutamate Release in the Rat Visual Cortex. Li, Y.H., Han, T.Z. J. Neurophysiol. (2007) [Pubmed]
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