The Role of NMDA Receptor on Spatial Learning and Memory Consolidation Rat Following Intra-Hippocampal Injection of Aqueous Extract of Leaves of Origanum (Origanum Vulgare L. ssp. viridis)

Intra-hippocampal adminestration of origanum (ORG) improves spatial learning of rats. The aim of the present study was to investigate the possible mechanism for origanum extract on spatial learning and memory in the hippocampus. In this study 42 adult male Wistar rats were used. Animals were cannulated bilaterally in the posterior laterl of hippocampus. After the recovery period, the spatial learning and memory were assessed using Morris Water Maze (MWM). Saline, ORG (0.03μg/site) glutamate receptor antagonist MK801 (0.08, 0.2 and 0.4 μmol/site) and co-injected of MK + ORG was injected into the posterior lateral of hippocampus 20 minutes before the training and retrival sesions (for 5 consecutive days) (n =7). The results showed that the intra-hippocampal injection of MK 801 significantly blocked the decreased distance and time of reaching (due to ORG injection) to find hidden platform of MWM (p <0.05). On the retrival tests, the average of time spent in the target area is reduced in the co-injected of MK801 + ORG group. The intra-hippocampal injection of aqueous extract of origanum may improve working memory in rats through glutamate-dependent NMDA receptors.