NITRIC-OXIDE IS INVOLVED IN THE FORMATION OF LEARNING AND MEMORY IN RATS - STUDIES USING PASSIVE-AVOIDANCE RESPONSE AND MORRIS WATER MAZE TASK

The study was designed to test whether blockade of endogenous NO produ ction affects learning and memory formation in rats. The rats received an intracerebroventricular (i.c.v.) injection of the inhibitor of nit ric oxide synthase, N-omega-nitro-L-arginine (NAME), 30 min before eac h training, and were then tested in the one-trial passive avoidance re sponse and Morris water maze task, respectively. The results showed th at: (1) among four concentrations of drug used, only doses higher than 3 mu mol of i.c.v. NAR?IE impaired learning and memory formation sign ificantly (p < 0.05) in both test models; (2) in Morris water maze tas k, the animals treated with highest dose of NAME (5 mu mol) failed to learn while those treated with lower doses succeeded; (3) in Morris wa ter maze task, the i.c.v. NAME, even in higher doses, did not affect t he capacity of finding a visible platform. It is suggested that NO is involved in learning and memory formation by potentiating or facilitat ing mainly the acquisition process.