The Effect of Nitric Oxide Precursor (L-Arginine) and Inhibitor (L-NAME) in Nucleus Accumbens on Learning and Memory in Stressed Rats

OBJECTIVES: This study investigates the effect of nucleus accumbens nitrergic system manipulation on learning and memory under stress conditions, using precursor (L-Arginine) and inhibitor (L-NAME) of Nitric Oxide. METHODS: Cannulation was performed in the brain nucleus accumbens shell of 120 Wistar rats. Saline and various dosages of L-Arg and N(omega)-Nitro-L-Arginine Methyl Ester (L-NAME) at 1, 5, and 10 mu g/rat dose administered in the nucleus accumbens according to grouping. After five minutes, the stress groups received an electric foot shock for four consecutive days (according to the protocol), but the non-stressed groups did not receive any shock. Corticosterone levels were measured on the first and fourth days. The Barnes maze test measured learning and memory in the following. RESULTS: Stress raised corticosterone substantially, whereas NO modulation lowered it at 10 mu g/rat dosage. Both the stress group (positive control) and the groups with injection of NO modulation without stress circumstances showed a decrease in errors during the learning phase. Long-term memory was also improved by stress and L-Arg at a dose of 5 mu g/rat. The effects of L-NAME on memory were attenuated at a dosage of 5 mu g/rat. The L-Arg-treated rats continued using serial or direct movement strategies well into the longterm memory phase. The beneficial effects of 1 mu g/rat of L-Arg on long-term memory were attenuated by stress, whereas the adverse effects of 5 mu g/rat of L -NAME were amplified. CONCLUSION: Due to its effectiveness in lowering mistake rates, the stress we used in this investigation may be eustress. L-Arg enhances cognitive performance and memory retention whereas L -NAME has the opposite effect. Additionally, modest doses of L-Arg enhanced stress' beneficial impact on memory, but L-NAME reduced it.