The effect of ACPD on the responses to NMDA and AMPA varies with layer in slices of rat visual cortex.

The effect of 1S,3R-aminocyclopentane dicarboxylic acid (ACPD) was measured on cells from various layers in slices of the rat visual cortex using whole-cell recording techniques. The position of the recorded cell was estimated by distance from pia to the layer VI/white matter boundary, and verified in 34/97 cells by staining with biocytin. Potentiation or depression of the responses to NMDA and AMPA by the metabotropic glutamate agonist ACPD was examined by iontophoresis of the drugs close to the cell body. Iontophoresis of ACPD had different effects in different layers. In layer VI, ACPD produced a substantial depolarization, which augmented the responses to NMDA and AMPA. In layer V, ACPD did not produce a significant depolarization, but potentiated the response to NMDA and AMPA. In layer IV, ACPD produced a small hyperpolarization, and depressed the response to NMDA. In layers II and III, the results were small and variable. Most recordings from stained cells were from pyramidal cells. Where recordings from non-pyramidal cells were obtained (3/34), results were the same as from pyramidal cells in the same layer. The same results were obtained when tetrodotoxin was in the bath solution. We conclude that the potentiation or depression of the response to NMDA and AMPA by ACPD varies with layer in rat visual cortex. Copyright 1998 Elsevier Science B.V.