Behavioral activity of angiotensin II after stimulation of L-arginine/nitric oxide pathway in rats

This study was conducted to determine what, if any, role L-arginine [an endogenous donor of nitric oxide (NO)] plays in the behavioral changes induced by angiotensin II (AII) in rats. The motility, stereotypy, spatial learning performance, learning of conditioned avoidance response and retention of passive avoidance behavior allowing to avoid aversive stimulation were investigated. Saline (0.9% NaCl), AII, L-arginine and AII combined with L-arginine were injected 15 min before the experiment into lateral cerebral ventricles (icv). L-arginine significantly enhanced locomotor activity while the treatment with AIIplus L-arginine reduced number of bar approaches in the open field test. AII, L-arginine and AII combined with L-arginine (but not with D-arginine) significantly accelerated acquisition of conditioned avoidance responses and not significantly improved recall of the passive avoidance. Only L-arginine displayed a tendency to inhibit acquisition of spatial learning on the second day of investigation in the Morris water maze. AII, L-arginine and AII with L-arginine applied immediately before the experiment intensified stereotypy evoked by apomorphine at a dose of 1 mg/kg and amphetamine at a dose of 7.5 mg/kg given intraperitoneally. These results showed that: 1) L-arginine as a donor of NO might be involved in memory and learning processes, 2) overproduction of NO did not change behavioral effects of AII in these experiments.