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

Abstract

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.Nitric oxide (NO), a gas molecule generated endogenously from the amino acid L-arginine by nitric oxide synthase (NOS), is a freely diffusible intercellular messenger that functions in various cells in the nervous system. In the hypothalamo-neurohypophysial system, NO mediates neuronal synaptic transmission and plasticity in the regulation of vasopressin and oxytocin secretion (16,17). As the important neuroendocrine cells, the supraoptic nuclei (SON) and paraventricular nuclei (PVN), as well as in their axon terminals in the neural lobe, synthesizes vasopressin and oxytocin in response to osmotic alternations in physiological and pathophysiological states (2,16 Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errorsmaybe discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. reported in the entire hypothalamo-neurohypophysial system (18,30). As a marker of NOS activity, NADPH-diaphorase was reported to reside in this system (2,23). The activated NO system was reported to involve the response of magnocellular neurons to acute and chronic osmotic insults, such as dehydration and hypovolemia (17,18,30). These studies indicate that disturbances of fluid balance triggered the system to prod...

Melatonin ameliorates hippocampal nitric oxide production and large conductance calcium‐activated potassium channel activity in chronic intermittent hypoxia

“…The membrane and cytosolic protein extractions were performed by using the ProteoExtract™ Native Membrane Protein Extraction Kit (Calbiochem, San Diego, CA, USA) and immunoblotting of NOS and BK channel proteins were described elsewhere [34–36]. Briefly, the SD rats were deeply anesthetized and decapitated.…”

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“…As noted above, CO can modulate the activity of soluble guanylate cyclase and, in tissues in which both NOS and HO are expressed, HO activity can suppress cGMP levels , thus interfering with NOS signalling at targets downstream to NOS, without changing NO bioavailability. In this context, however, it is important to acknowledge that, although several studies support a link between NO and the sCG‐cGMP pathway , alternative pathways have also been demonstrated, such as S‐nitrosylation .…”

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