Scopolamine injected into the rat amygdala impairs working memory in the double Y-maze

Recent neurochemical results suggest the hypothesis that the nucleus basalis magnocellularis (nbm) cholinergic projection to the amygdala may play a role in memory. The present study investigated the effects of intra-amygdaloid injections of the cholinergic antagonist scopolamine on working and reference memory in the double Y-maze. Rats were pretrained until working and reference memory choice accuracy stabilized to a criterion of > or = 86% correct. Bilateral cannulae were then surgically implanted in the basolateral amygdaloid complex. Rats (n = 9) received scopolamine in doses of 8.0, 24.0, and 72.0 micrograms/0.5 microliter and saline (0.5 microliter) in a counterbalanced order with retraining to criterion between injections. Intra-amygdaloid scopolamine produced a dose-dependent and differential impairment of working and reference memory. A dose of 24.0 micrograms impaired working memory without significantly affecting reference memory; doses of 8.0 micrograms and 72.0 micrograms affected neither and both types of memory, respectively. Results implicate amygdaloid acetylcholine in memory.