Involvement of the medial precentral pre-frontal cortex in memory consolidation for inhibitory avoidance learning in rats

Adult male Wistar rats were trained in a step-down inhibitory avoidance lea rning task (3.0-s, 0.4-mA foot shock), received a 0.5-mu l infusion of musc imol (0.02, 0.1, or 0.5 mu g), AP5 (0.16, 0.34, 0.5, 1.6, or 5.0 mu g), SCH 23390 (0.05, 0.34, 0.5, or 1.75 mu g), 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 mu g), AP5 (0.34 or 0.5 mu g), or SCH (0.5 or 1.75 mu g) were amnesic. Then, animals were infu sed with muscimol (0.1 or 0.5 mu g), AP5 (0.34, 0.5, or 5.0 mu g), or SCH ( 0.5 mu g) at other posttraining times and/or into the junction of Fr1-Fr2 ( CII). Muscimol (0.1 and 0.5 mu g) or SCH into CI were amnesic when given 90 or 180 min after training, but not when given 270 min after training. Musc imol (0.5 mu g, but not 0.1 mu g) or SCH into CII were amnesic when given 9 0 min after training, but not when given 0 or 180 min after training. AP5 ( 0.5, but not 5.0 mu g) 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 a t 90 min posttraining. The results suggest that 1) the glutamatergic, GABAe rgic, and dopaminergic systems in Fr2 are involved in the consolidation of memory for inhibitory avoidance learning, either directly or as parts of mo dulatory systems; and 2) timing of involvement of anterior Fr2 (CI) is diff erent from that of posterior Fr2(CII). (C) 2000 Elsevier Science Inc.