The effect of L-arginine on Morris water maze tasks of ovariectomized rats.

The role of ovarian hormones, nitric oxide, and their interaction on learning and memory has been widely investigated. The present study was carried out to evaluate the effect of acute (A) and chronic (C) L-arginine (L-Arg) administration on learning and memory in ovariectomized (OVx) rats. Forty-five rats were divided into six groups: 1) sham, 2) OVx, 3) sham-L-Arg-A, 4) OVx-L-Arg-A, 5) sham-L-Arg-C, 6) OVx-L-Arg-C. The animals of sham-L-Arg-A and OVx-L-Arg-A were acutely treated with 500 mg/kg of L-Arg during 5 test days. Sham-L-Arg-C and OVx-L-Arg-C chronically received 500 mg/kg/day of L-Arg during 8 weeks before 5 test days. The animals in sham and OVx groups received 1 ml/kg saline instead of L-Arg. At the end of the experiment, the animals were tested in Morris water maze and the escape latency and traveled path to reach the platform were compared between groups. Results showed that the escape latency and traveled path in OVx group were significantly higher than in sham group ( p <0.05). The animals in OVx-L-Arg-A group had significantly lower traveled path length and escape latency compared to OVx group ( p <0.001). Chronic treatment by L-Arg had no significant effect on learning and memory in OVx and sham-operated animals. It seems that L-Arg has a role in Morris water maze tasks disturbances in OVx rats but it needs to be further investigated.