Effects of L-arginine on 7-nitroindazole-induced reference and working memory performance of rats.

BACKGROUND/AIMS This study was performed in order to elucidate the effects of 7-nitroindazole (7-NI) and L-arginine on cognitive functions of rats in a three-panel runway task. METHODS 7-NI (2.5, 5, 10 mg/kg) and L-arginine (200 mg/kg) were injected intraperitoneally into male Wistar rats 30 min before the test. RESULTS 7-NI (5, 10 mg/kg) significantly increased the number of errors (pushes made on the 2 incorrect panels of the panel gate at 4 choice points) and prolonged the latency of reference memory in the three-panel runway task. The negative effects of 7-NI on reference memory was counteracted by L-arginine, a substrate for nitric oxide synthase. While having no effect on the number of working memory errors in working memory trials, 7-NI prolonged the latency from the 2nd to the 6th trial at the 5- and 10-mg/kg doses. Concurrent administration with L-arginine counteracted the 7-NI-induced prolongation of latency from the 2nd to the 6th trial. CONCLUSION 7-NI impaired reference memory but not working memory in the three-panel runway test. Moreover, nitric oxide played an essential role in the development of reference memory and the negative effects of 7-NI on memory were counteracted by L-arginine.