Upregulation of Orexin in the Paraventricular Nucleus Contributes to Salt Sensitive Hypertension

Orexin and orexin receptors are extensively expressed in the hypothalamic paraventricular nucleus (PVN) and the hyperactivity of PVN orexin contributes to increased sympathetic nerve activity (SNA) and elevated blood pressure in several animal models. However, the role of PVN orexin in the development of salt sensitive hypertension (SSHTN) is unknown. In this study, we tested the hypothesis that PVN orexin expression is increased in SSHTN and contributes to the development of SSHTN via regulating vasopressin secretion. Eight-week-old Dahl salt sensitive (DS) rats were divided into two groups and were fed either a high salt (HS, 8% NaCl) or normal salt (NS, 0.4% NaCl) diet. Six weeks following diet treatment, rats were anesthetized and their mean arterial pressure (MAP) and sympathetic nerve activity (SNA) response to orexin receptor blockade were recorded. In a separate group of rats PVN orexin mRNA levels were measured. The results showed that HS intake induced significant increases in MAP (HS: 146±2 vs....