Possible role of nitric oxide in the locomotor activity of hypertensive rats

We aimed to analyze whether hypertension and changes in nitric oxide (NO) generation are associated with alterations of locomotor activity in rats. Male Wistar rats treated with an inhibitor of NO synthase, NG-nitro-L-arginine methyl ester (L-NAME, 40 mg/kg/day) for 6 weeks, control Wistar rats, spontaneously hypertensive rats (SHR), and control Wistar Kyoto rats (WKY) aged 18 weeks were investigated. Locomotor activities were tested by the open field method. NO synthase activity (NOS), concentration of cGMP and conjugated dienes (CD) as well as protein expression of nuclear factor NF-kappaB were determined in the cerebral cortex, cerebellum and brainstem. NOS activity in the brain parts investigated was not changed in SHR in comparison with the normotensive WKY. L-NAME treatment resulted in the decreased NOS activity in comparison with Wistar rats. The concentration of CD and expression of NF-kappaB protein, markers of reactive oxygen species, were higher and the concentration of cGMP was lower in hypertensive animals and more pronounced in SHR as well. Thus, the concentration of NO in the brain parts of SHR might be lower than in the L-NAME treated rats. L-NAME treatment increased horizontal (by 28%) and vertical (by 80%) motor activity. Similarly, in SHR both locomotor activities were increased by 105% and 148%, respectively, in comparison with WKY. In conclusion, decreased level of NO was associated with increased locomotor activity indicating that in addition to genetic differences which may determine changes in locomotor activity in hypertensive rats, the role of a signalling pathway mediated by NO may be supposed.