Presynaptic inhibitory action of a metabotropic glutamate receptor agonist on excitatory transmission in visual cortical neurons

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Abstract
A family of metabotropic glutamate receptors (mGluRs) has been elucidated by molecular cloning. To study the possible modulatory role of mGluRs in synaptic transmission, we tested the effect of a mGluR agonist, ($\pm $)-l-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD), on the excitatory post-synaptic currents (EPSCs) recorded from neurons in thin slices of rat visual cortex, by using the whole-cell patch-clamp method. We found that trans-ACPD markedly suppressed the evoked EPSCS without affecting the mean amplitude of spontaneous miniature EPSCS. This effect on the evoked EPSCS was blocked by a potassium channel blocker, 4-aminopyridine (4-AP) in a dose-dependent manner We suggest that trans-ACPD presynaptically inhibits EPSCS by a mechanism involving the 4-AP-sensitive channels.