OPIOID MODULATION OF WORKING-MEMORY - INTRASEPTAL, BUT NOT INTRAAMYGDALOID, INFUSIONS OF BETA-ENDORPHIN IMPAIR PERFORMANCE IN SPATIAL ALTERNATION

The effect of beta-endorphin on spatial working memory was examined fo llowing microinfusions of beta-endorphin into the medial septal area a nd central amygdaloid nucleus in Long-Evans male rats. Working memory was assessed by spatial alternation in a T-maze. beta-Endorphin, 250 a nd 1000 ng/site, respectively, and muscimol, 20 ng/site, were infused into the medial septal area or central amygdaloid nucleus prior to beh avioral testing. The hippocampal theta rhythm was examined following i ntraseptal infusions of beta-endorphin and muscimol. In the medial sep tal area, beta-endorphin and muscimol impaired choice accuracy and red uced the power of hippocampal theta rhythm. The degree of reduction in the power of hippocampal theta rhythm was correlated with the magnitu de of behavioral impairment of choice accuracy in spatial alternation. In the central amygdaloid nucleus, beta-endorphin (1000 ng) and musci mol (20 ng) did not affect choice accuracy. The results suggest that s eptal, but not amygdaloid, opioid, and GABAergic activity modulate spa tial working memory and hippocampal physiology. (C) 1995 Academic Pres s, Inc.