CB1 ligands modulate learning and memory of OBX rats

Purpose. The brain endocannabinoid system has been shown to play a role in learning and memory processes, although the exact mechanisms by which it interferes in these processes are not well established. We aimed at studying the effects of CB1 receptor ligands on learning and memory of rats with an experimental model of depression - olfactory bulbectomy (OBX). Material and methods. Cannabinoid CB1 receptor agonist HU-210 (5 µg) and cannabinoid CB1 receptor antagonist SR 141716A (3 µg) were microinjected i.c.v. in male Wistar rats with olfactory bulbectomy (OBX) model of depression. A passive avoidance task (step through) was used as a test for learning and memory. Results. In the non-OBX group, HU-210 impaired learning and memory processes expressed by the shortened latency time on the retention tests (3 hours and 24 hours after training) and by the decreased percentage of rats that have reached the learning criterion, as compared to the saline-treated controls. SR 141716A did not affect significantly the performance of rats in the step-through task. In the OBX rats HU-210 prolonged the latency time as compared to the saline-treated OBX controls, while SR 141716A did not affect significantly the OBX-related learning and memory deficits. Conclusion. These findings suggest complex modulatory effect of CB1 receptor agonist on learning and memory processes in non-OBX and OBX rats.