Effects of restraint stress and nitric oxide synthase inhibition on learning and strategy preference in young adult male rats.

Objective: The aim of this study was to investigate the effects of restraint stress and nitric oxide synthase (NOS) inhibition by NωNitro-L-Arginine (LNA) on learning and strategy preference.

Material And Methods: Rats were randomly divided into four groups (Saline, Saline+Stress, LNA, LNA+Stress). Stress was applied for one hour in glass cylinders during 13 days. One hour after this stress application, water maze experiments were started. Injections (saline 1 ml/kg or 50 mg/kg LNA) were given 10 minutes before each experiment. The platform was kept visible or hidden (on the 4(th), 8(th), 12(th) days) at the same position. On the 13(th) day the platform was located on the opposite quadrant.

Results: Saline groups exhibited significantly better performances (F(1.31)=174.038 p<0.05) at the beginning compared to the NOS inhibited groups. For initial hidden platform days; stress was determined as an impairment factor (F(1.31)=5.190 p=0.012). At the end, acquisition occurred on both visible and hidden platform days for all groups. There was no significant strategy preference difference between the groups.Development of the stress and NOS inhibition impairments were seen, particularly at different periods of the acquisition.

Conclusion: NOS inhibition did not worsen restraint stress-induced learning impairments in rats. Lack of effect may be explained by the antidepressive consequences of NOS inhibition.