THE GROUP-III METABOTROPIC GLUTAMATE-RECEPTOR AGONIST, L-AP4, REDUCESEPSPS IN SOME LAYERS OF RAT VISUAL-CORTEX

The action of the specific Group III metabotropic glutamate receptor, L-2-amino-4-phosphonobutanoic acid (L-AP4) was tested in slices of rat visual colter. When the predominant input to the cell was stimulated, L-AP4 generally reduced the EPSP that was produced. This result was s pecific to the layer: it was found when recording cells in layers II/I II, V and VI, but not when recording cells in layer rv. The effect was the same when G-proteins in the cell recorded were inactivated. Also, L-AP4 had Little effect on membrane potential and input impedance of the cell recorded, and little effect on the response to NMDA in that c ell. Thus, Group LII metabotropic glutamate receptors act presynaptica lly to reduce the release of glutamate onto cells in layers II/III, V and VI in visual cortex, but not cells in layer IV. (C) 1998 Elsevier Science B.V. All rights reserved.