Interaction between neuronal nitric oxide synthase and inducible nitric oxide synthase after traumatic brain injury in rats

Abstract

Objective To study the mechanism of interaction between neuronal nitric oxide syn-thase (nNOS) and inducible nitric oxide synthase (iNOS) following traumatic brain injury (TBI) in rats. Methods A total of 250 male Wistar rats were randomly divided into five groups, ie, sham oper-ation group, trauma group, 7-nitroindazole (7-NI) treatment group, aminoguanidine (AG) treatment group and combined AG and 7-NI treatment group. Severe closed TBI was made by using Marmarou meth-od. Protein expressions of nNOS and iNOS in hippocampus CAI were detected by means of immunohisto-chemical staining at 1,3, 6, 12 hours and at days 1,3, 7 and 14 after TBI. Results The expression of nNOS reached a peak at 6 hour after injury in all groups, with no statistical difference between groups (P > 0. 05), when there was no statistical difference between 7-NI treatment group and trauma group (P > 0. 05) but statistical difference in AG treatment group and combined AG and 7-NI treatment group compared with trauma group at 12 hours after TBI (P <0.05). The expression of iNOS reached maximal level at day 3 after TBI, with lower level in 7-NI group, AG treatment group and combined AG and 7-NI treatment group compared with trauma group (P < 0.05). Conclusions After TBI, nNOS interacts with iNOS by means of the feedback of nitric oxide. The enhanced expression of nNOS is initial factor for increase of iNOS expression, which can down regulate the expression of iNOS. Key words: Brain injuries; Nitric oxide synthase; Rats