AMYGDALA BETA-NORADRENERGIC INFLUENCES ON MEMORY STORAGE INVOLVE CHOLINERGIC ACTIVATION

These experiments examined the involvement of the amygdaloid complex a s a site of interaction of adrenergic and muscarinic cholinergic influ ences on memory storage. Male Sprague-Dawley rats (60 days old; 250-30 0 g) were given a single training trial in an inhibitory avoidance tas k and a retention test trial 48 h later. Immediately after training bu ffer control or drug solutions (0.5 mu l) were infused into the amygda la and, in the first experiment only, other drugs were administered in traperitoneally (ip). The first experiment examined the effects of pos t-training systemic injections of the muscarinic agonist oxotremorine (100.0 mu g/kg) administered alone or together with intra-amygdala inj ections of either the muscarinic antagonist atropine (1.0 mu g) or the beta-noradrenergic antagonist propranolol (0.3 mu g). Oxotremorine en hanced retention and atropine, but not propranolol, attenuated the eff ects of oxotremorine. In the second experiment intraamygdala infusions of the beta-noradrenergic agonist clenbuterol (10.0 ng) were administ ered either alone or together with atropine (1.0 mu g). Clenbuterol en hanced retention and atropine blocked the effects of clenbuterol. In t he third experiment intraamygdala infusions of oxotremorine (3, 10, 30 , or 100 ng) were administered either alone or together with propranol ol(0.3 mu g). Oxotremorine (3.0 and 10.0 ng) enhanced retention and pr opranolol did not block the effects of oxotremorine. These findings ar e consistent with the view that memory storage is regulated by an inte raction of beta-noradrenergic and cholinergic influences and suggest t hat the noradrenergic influences are mediated by the release of acetyl choline and activation of muscarinic cholinergic receptors within the amygdala. (C) 1996 Academic Press, Inc.