The Stabilization of Central Sympathetic Nerve Activation by Renal Denervation Prevents Cerebral Vasospasm after Subarachnoid Hemorrhage in Rats

Abstract

The poor prognosis of subarachnoid hemorrhage (SAH) might be associated with sympathetic nerve activation (catecholamine surge) initiated by hypothalamic injury. As renal denervation (RD) has been shown to exert protective effects on cardiovascular dysfunction by suppressing increased central sympathetic nerve activation, we examined whether RD improved the experimental SAH prognosis in this study. Two hundred thirty-eight male Sprague-Dawley rats were divided into sham-operated and SAH-operated groups, and then each rat was further separated into Sham-operated and RD-operated groups. Bilateral RD was performed approximately 45\xa0min after SAH induction. We examined the effect of RD on early brain injury (EBI) and delayed cerebral ischemia (DCI) as a primary endpoint, and also explored the effect on cerebral vasospasm (CVS) as a secondary endpoint. Although RD did not exert significant effects on primary endpoint, RD significantly prevented CVS and reduced SAH-induced increases in the number of phosphorylated extracellular signal-regulated kinase (ERK)-positive endothelial cells, cyclooxygenase-2 expression, and macrophage infiltration in major cerebral arteries. Moreover, RD significantly decreased the areas displaying dopamine β-hydroxylase and glial fibrillary acidic protein immunopositivity in the paraventricular nucleus of the hypothalamus and serum angiotensin II levels, all of which were increased by SAH. Although RD decreased systolic blood pressure, significant changes in cerebral blood flow were not observed compared with SAH\u2009+\u2009Sham group. Based on the findings, RD improved CVS by reducing endothelial cell damage and the effects were associated with the stabilization of central sympathetic nerve activation in a SAH model.