The Role of Intrahippocampal Microinjections of Anisomycin on Dexamethasone-Induced Modulation of Memory Consolidation in Rats

Evidence indicates that hipppocampus and activation of glucocorticoid receptors in this area are necessary for emotional learning and memory processes also some studies suggest that glucocorticoid’s effects probably involve with processes of protein synthysis in the hippocmapus. The aim of this study was to determine the role of intrahippocampal microinjections of anisomycin [(ANS) as a protein synthysis inhibitor)] on dexamethasone-induced modulation of memory consolidation in the passive avoidance learning (PAL) task in rats. In this study, 90 male Wistar rats (250–300 gr) were surgically implanted bilaterally with cannulae aimed at the dorsal hippocampus (DH) were trained in PAL task. In experiment 1. Dexamethasone (0.1, 0.5, 1 and 3 mg/kg IP) was injected immediately after training and vehicle injected into DH. In experiment 2. Anisomycin (0.5, 1 µg/µl/side) or vehicle were injected bilaterally into the DH followed immediately by IP injection of Dexamethasone (1 mg/kg) or vehicle. Two days after training, retention tests were done and step-through latency (STL) and total time spent in light chamber (TLC) of apparatus were recorded during 10 min and compared with controls. Data indicated that injection of Dexamethasone immediatly after training enhanced memory consolidation (P<0.01) and this effect was blocked by injection of ANS in to the DH (P<0.01). The findings above showed that glucocorticoids play on important role in consolidation of emotional learning and probably in processes of protein synthesis in the hippocampus may play an important role in mediating these effects.