Pyramidal

We have shown previously that a selective metabotropic glutamate receptor (mGluR) agonist, 1S,3R-1-aminocyclo-pentane-1,3-dicarboxylate (1S,3R-ACPD), evokes an inward current in CA1 pyramidal neurons of rat hippocampal slices in the presence of K1 channel blockers (Crépel et al., 1994). This current has been characterized as a Ca21-activated nonselec-tive cationic (CAN) current. Using whole-cell patch-clamp re-cordings and intracellular dialysis, we now have identified the mGluR subtype and the mechanisms underlying the CAN cur-rent (ICAN) and report for the first time the presence of a synaptic ICAN in the mammalian CNS. First, we have shown pharmacologically that activation of ICAN by 1S,3R-ACPD in-volves the group I mGluRs (and not the groups II and III) and a G-protein-dependent process. We also report that ICAN is mod-ulated by the divalent cations (Mg21, Cd21, and Zn21). Sec