Involvement of the Medial Precentral Prefrontal Cortex in Memory Consolidation for Inhibitory Avoidance Learning in Rats

Abstract

MELLO E SOUZA, T., M. R. M. VIANNA, C. RODRIGUES, J. QUEVEDO, B. A. MOLETA AND I. IZQUIERDO. Involvement of the medial precentral prefrontal cortex in memory consolidation for inhibitory avoidance learning in rats. PHARMACOL BIOCHEM BEHAV 66(3) 615–622, 2000.—Adult male Wistar rats were trained in a step-down inhibitory avoidance learning task (3.0-s, 0.4-mA foot shock), received a 0.5-μl infusion of muscimol (0.02, 0.1, or 0.5 μg), AP5 (0.16, 0.34, 0.5, 1.6, or 5.0 μg), SCH 23390 (0.05, 0.34, 0.5, or 1.75 μg), saline, or vehicle (DMSO 20%) into the anterior medial precentral area (Fr2) (CI) immediately after training, and were tested 24 h later. Muscimol (0.02, 0.1, or 0.5 μg), AP5 (0.34 or 0.5 μg), or SCH (0.5 or 1.75 μg) were amnesic. Then, animals were infused with muscimol (0.1 or 0.5 μg), AP5 (0.34, 0.5, or 5.0 μg), or SCH (0.5 μg) at other posttraining times and/or into the junction of Fr1–Fr2 (CII). Muscimol (0.1 and 0.5 μg) or SCH into CI were amnesic when given 90 or 180 min after training, but not when given 270 min after training. Muscimol (0.5 μg, but not 0.1 μg) or SCH into CII were amnesic when given 90 min after training, but not when given 0 or 180 min after training. AP5 (0.5, but not 5.0 μg) was amnesic when given into CI, but not into CII, at 0 or 180 min posttraining, and a trend toward an amnesic effect was seen at 90 min posttraining. The results suggest that 1) the glutamatergic, GABAergic, and dopaminergic systems in Fr2 are involved in the consolidation of memory for inhibitory avoidance learning, either directly or as parts of modulatory systems; and 2) timing of involvement of anterior Fr2 (CI) is different from that of posterior Fr2 (CII).