ACTIVATION OF METABOTROPIC GLUTAMATE RECEPTORS HAS DIFFERENT EFFECTS IN DIFFERENT LAYERS OF CAT VISUAL-CORTEX

Single neurons were recorded in cat primary visual cortex, and the eff ect of iontophoresis of the metabotropic glutamate agonist 1S,3R-amino cyclopentane-1,3-dicarboxylic acid (ACPD) was observed. In nearly all cases (41/43), ACPD reduced the visual response. In some cases ACPD al so reduced spontaneous activity (24/43), and in other cases ACPD incre ased spontaneous activity (18/43). Increases were generally seen in in fragranular layers (V and VI), and decreases in supragranular layers ( II and III). The reduction in the visual response was also largest in supragranular layers. We conclude that activation of metabotropic glut amate receptors has both facilitatory and depressive effects in visual cortex, and the effect depends on the layer of the cell recorded.