Effects of nitric oxide on expressions of nitrosocysteine and calcium-activated potassium channels in the supraoptic nuclei and neural lobe of dehydrated rats.

Nitric oxide (NO) is an important gas mediator in the signal transduction cascade regulating osmotic function in the hypothalamo-neurohypophysial system. We previously found that increased nitric oxide synthase (NOS) activity in the supraoptic nuclei (SON) and neural lobe following osmotic stimulation and NO could regulate the expression of Ca(2+)-activated K(+) channel (BK channels) protein in the magnocellular system during dehydration. The aim of the current study is to examine the role of NO in the regulation of nitrosocysteine and BK channel protein in the magnocellular system in dehydrated animals. Using Western blot analysis and quantitative immunofluorescent staining study, we found that water deprivation in rats significantly enhanced the expression of nitrosocysteine protein in SON and neural lobes. Immunohistochemistry study indicated that dehydration significantly increased the profiles of SON neurons co-expressing nitrosocysteine with BK-channel protein. Intracerebroventricular administration of L-NAME (an inhibitor of NO synthase) significantly reduced the neuronal profiles of nitrosocysteine, as well as their co-expression with BK-channel in SON of dehydrated rats. However, treatment of sodium nitroprusside (a donor of NO) increased this co-expression. Our results indicate that NO signaling cascade may control the expression of BK channels through the regulation of nitrosocysteine in SON and neural lobe of rats during osmotic regulation.