Introduction: This study was conducted to determine the possible beneficial results of L-arginine on prefrontal cortex of rats which impressed by immobilization stress to define the synchronous impression of stress and nitric oxide (NO) on evolution of prefrontal cortex of rats after birth.

Methods: Forty-eight one month, male Wistar rats were divided into two groups: stressed and non-stressed. L-Arginine (200 mg/kg) as a NO synthase (NOS) inducer and L-NAME (2O mg/kg) were injected intraperitonealy (IP) and 7- nitroindazde (25 mg/kg) as non-specific was injected subcutaneously (S.C.) for 4 weeks. The kind of stress was immobilization for 4 weeks, every other day. The brain was removed after this period and each brain divided into two parts in a coronal section manner. Anterior part used for histological studies with H&E staining and posterior part used for measurement of NO production using spectrophotometer at 540 nm wavelengh.

Results: Statistical analysis of microscopic and light microscopic finding showed that thickness of prefrontal cortex and NO production were significantly decreased in stressed rats and especially in groups which received 7- nitroindazole and L-NAME and L-arginine could reverse these results.

Discussion: According to this research, we could say that L-arginine decreases the cortical damages in stressed rats and 7-nitroindazole and L-NAME increase this damage in non-stressed group. Although in non stressed groups, L-arginine, L-NAME and 7- nitroindazole were all non-protective and damaging.