BACKGROUND:Nitric oxide (NO) exhibits both protective and detrimental effects in the central nervous system.OBJECTIVE:To investigate the effect of NO on the prefrontal cortex in neonatal stressed rats.DESIGN, TIME AND SETTING:A randomized, controlled, animal study was performed at the Anatomical Department of Iran University of Medical Sciences from May 2007 to August 2008.MATERIALS:Forty-eight male, Wistar rats were obtained from Pasteur’s Institute, Tehran, Iran.METHODS:Rat stress models were established by immobilization and randomly received intraperitoneal injection of 2 mL physiological saline, L-arginine (200 mg/kg) as a NO precursor, N(G)-nitro-L-arginine methyl ester (20 mg/kg), or subcutaneous injection of 7-nitroindazole (25 mg/kg) as a NO synthase inhibitor.MAIN OUTCOME MEASURES:After the rats were treated for 4 weeks, the frontal cortex was harvested for histological observation and NO detection.RESULTS:Subcutaneous administration of N(G)-nitro-L-arginine methyl ester or 7-nitroindazole resulted in significantly lower prefrontal cortex thickness and NO production compared with subcutaneous administration of L-arginine (P<0.05).Prefrontal cortex thickness significantly increased in rats following L-arginine treatment, compared with physiological saline intervention (P<0.05).CONCLUSION:NO exhibited protective effects on the prefrontal cortex of stressed rats. BACKGROUND: Nitric oxide (NO) exhibits both protective and detrimental effects in the central nervous system. OBJECTIVE: To investigate the effect of NO on the prefrontal cortex in neonatal stressed rats. DESIGN, TIME AND SETTING: A randomized, controlled, animal study was performed at the Anatomical Department of Iran University of Medical Sciences from May 2007 to August 2008. MATERIALS: Forty-eight male, Wistar rats were obtained from Pasteur’s Institute, Tehran, Iran. METHODS: Rat stress models were established by immobilization and holds received intraperitoneal injection of 2 mL of physiological saline, L-arginine as a NO precursor, N (G) -nitro-L-arginine methyl ester (20 mg / kg), or subcutaneous injection of 7-nitroindazole / kg) as a NO synthase inhibitor. MAIN OUTCOME MEASURES: After the rats were treated for 4 weeks, the frontal cortex was harvested for histological observation and NO detection.RESULTS: Subcutaneous administration of N (G) -nitro-L-arginine methyl ester or 7 -nitroindazole resulted in significantly lower prefrontal cortex thickness and NO production compared with subcutaneous administration of L-arginine (P <0.05) .Prefrontal cortex thickness significantly increased in rats following L-arginine treatment, compared with physiological saline intervention (P <0.05). CONCLUSION: NO indicated protective effects on the prefrontal cortex of stressed rats.