Salusin beta Within the Nucleus Tractus Solitarii Suppresses Blood Pressure Via Inhibiting the Activities of Presympathetic Neurons in the Rostral Ventrolateral Medulla in Spontaneously Hypertensive Rats

摘要

Salusin beta is a newly identified bioactive peptide, which shows peripheral hypotensive, mitogenic and proatherosclerotic effects. The present study was undertaken to investigate the role of salusin beta within the nucleus tractus solitarii (NTS) and the underlying mechanism in regulating blood pressure and heart rate (HR) in spontaneously hypertensive rats (SHR). Our results showed that bilateral or unilateral microinjection of salusin beta (0.4-40 pmol) into the NTS in SHR decreased mean arterial pressure and HR in a dose-dependent manner. Bilateral microinjection of salusin beta (4 pmol) within NTS improved baroreflex sensitivity functions in SHR. Pretreatment with glutamate receptors antagonist kynurenic acid (5 nmol) into the NTS in SHR did not alter the salusin beta (4 pmol) induced hypotension and bradycardia. Likewise, bilateral vagotomy also did not alter the salusin beta (4 pmol) induced hypotension and bradycardia. However, pretreatment with GABA(A) receptors agonist muscimol (100 pmol) within the rostral ventrolateral medulla (RVLM) in SHR almost completely abolished the hypotension and bradycardia evoked by intra-NTS salusin beta (4 pmol). Our findings suggested that microinjection of salusin beta into the NTS produced hypotension and bradycardia, as well as improved baroreflex sensitivity functions, via inhibiting the activities of presympathetic neurons in the RVLM in SHR.