Anticonvulsant action of metabotropic glutamate receptor agonists in kindled amygdala of rats.

1S,3R-1-Aminocyclopentane-1,3-dicarboxylate (1S,3R-ACPD) and L-2-amino-4-phosphonobutyrate (L-AP4) are selective agonists of metabotropic glutamate receptors (mGluRs). 1S,3R-ACPD (200 nmol) injected into the amygdala (AM) of non-kindled rats produced immediate and transient seizures, characterized by immobility, searching, and wet-dog shakes. However, this ictal response was not observed in AM-kindled rats. Intra-AM injection of 1S,3R-ACPD (40 or 200 nmol) or L-AP4 (200 nmol) resulted in a delayed and marked suppression of kindled seizures, 3 days after 40 nmol of 1S,3R-ACPD, 1 day after 200 nmol of 1S,3R-ACPD, and from 1 to 3 days after 200 nmol of L-AP4. These and the previous findings suggest that: (1) the excitatory action of 1S,3R-ACPD in the AM, which may be mediated by the postsynaptic mGluRs, is reduced after completion of kindling; (2) 1S,3R-ACPD and L-AP4 exert anti-convulsant action in the AM, presumably by activating the presynaptic as well as postsynaptic mGluRs.