Effects of predator stress on nitric oxide and neuronal nitric oxide synthase in rat hippocampus

doi:10.3321/j.issn:1673-8225.2003.22.006

Abstract：AIM:To observe the changings of nitric oxide (NO) and the neuronal NOS (nNOS) in rats with posttraumatic stress disorder (PTSD)-like behaviors,in order to further explore the neurobiological mechanism in the pathogenesis of PTSD. METHODS:144 male Wistar rats were divided randomly into PS group for non injurious exposure of rats to cat for 10 min (n=72), and NC group for normal control (n=72).The nitric oxide (NO) and NO synthase (NOS) levels by neurochemistry methods,and the neuronal NOS (nNOS) expression by Western blotting in hippocampus and frontal cortex of experimental rats were investigated. RESULTS:The NO level in hippocampi of stressed rats with PTSD like behaviors was significantly increased immediately [(2.8± 0.8) μ mol/g,F=23.112,P=0.000],and reached the peak level at 12 h [(3.9 ± 1.1) μ mol/g,F=56.616,P=0.000 vs group NC;and F=14.917,P< 0.05 vs other interval in group PS],and still elevated at 24 h after predator stress [(2.6± 0.7) μ mol/g,F=23.094,P=0.000].The Western analysis demonstrated that the nNOS expression was markedly enhanced synchronously in hippocampus (compared with group NC,F=4.228, 21.772 and 18.500 for immediately,12 and 24 h after predator stress, respectively,P< 0.01), while the total NOS activity was only increased at 12 h after cat exposure [(9.8± 2.5) mmol/(s@ kg), F=32.812,P=0.000 and (10.2± 2.7) mmol/(s@ kg), F=31.395,P=0.000] for immediately and 12 h after predator stress,respectively. CONCLUSION:The lasting increased nNOS expression and NO releasing in hippocampus following severe psycophysiological stress may play an important role in the long -term PTSD like behavior in rats.