Down-regulation of alpha 2- and beta-adrenoceptor binding sites in rat cortex caused by amygdalar kindling

The role of central noradrenergic neurons in kindled seizures was assessed by comparison of alpha 2- and beta-adrenoceptor binding in the cerebral cortex from kindled and control rats. To minimize handling, which may modify kindling-induced changes in binding, the kindling protocol involved stimulation of the amygdala every hour for a maximum of 26 h. Twenty-four hours after kindling, down-regulation of beta-adrenoceptors was found in both olfactory cortex and the remaining neocortex, whereas alpha 2 down-regulation was confined to the olfactory cortex. At 21 days after kindling, the only change found was a down-regulation of beta-adrenoceptors in the neocortex. The results support the view that functional changes in central noradrenergic transmission are associated with the reduction in seizure threshold induced by kindling.