Amygdaloid NMDA and muscarinic receptors involved in working memory performance of rats.

In a three-panel runway task, the competitive N-methyl-D-aspartate (NMDA) receptor antagonist, 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid (CPP) (56 ng/side), injected bilaterally into the basolateral subdivision of the amygdala, significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel gates at four choice points) in a test of working memory. Intra-amygdaloid injection of the muscarinic receptor antagonist scopolamine (5.6 micrograms/side) also significantly increased working memory errors. In a test of reference memory, neither CPP nor scopolamine affected the number of errors when injected into the basolateral amygdala at doses up to 56 ng/side or 5.6 micrograms/side, respectively. These results indicate that processes mediated by NMDA and muscarinic receptors in the basolateral amygdala are involved in the performance of working memory, but not in reference memory.