The Role Of Salusin-β In Rostral Ventrolateral Medulla And It’s Pathogenesis In Septic Rats

Objective1. To determine the cardiovascular effect of microinjection of salusin-β into the rostral ventrolateral medulla (RVLM) in anesthetized rats, and study its mechanism.2. To investigate the distribution and content of endogenous salusin-β in septic rats.Methods1. Cardiovascular effects of salusin-β in RVLM:Thirty-two adult male Spargue-Dawley rats were enrolled in this study. The dose-dependant effects of salusin-β (0.04,0.4 and 4 pmol, respectively) on blood pressure and heart rate in the RVLM were determined by unilateral microinjection of salusin-β or artificial cerebrospinal fluid (aCSF) into the RVLM.2. Mechanism of salusin-β produces cardiovascular effects in RVLM:Thirty-five adult male SD rats were enrolled in this study. A non-selective glutamate receptor antagonist kynurenic acid (KYN,5 nmol, n=7), muscarinic receptor antagonist atropine (120 pmol, n=7), L-type calcium channels blocker nicardipine (Nic,200 pmol, n=7), non-selective nitric-oxide synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME,15 nmol, n=7) or aCSF (100 nl, n=7) have been applied into RVLM of rats 10 min before salusin-β (4 pmol) was microinjected to explore the signal transduction pathway of salusin-β.3. The distribution of salusin-β in tissues and serum levels:Thirty-six male SD rats were randomly divided into control group (n=9) with sham operation and experimental group (n=27) with septic rat model by cecal ligation and puncture (CLP). The model group rats were sacrificed after 6h,12h and 24h of treatment. The concentration of salusin-β in spleen, stomach, small intestine, hypothalamus and serum specimens were detected by enzyme-linked immunosorbent assay (ELISA).Results1. Cardiovascular effects of salusin-β in RVLM:Compared with aCSF group, unilateral microinjection of salusin-β into the RVLM produced a dose-dependant increase in blood pressure (BP) and heart rate (HR) (P<0.05).2. Mechanism of salusin-β produces cardiovascular effects in RVLM:Prior application of the L-NAME into the RVLM of rats did not alter the tachycardia and hypertension induced by intra-RVLM salusin-β(4 pmol). Notablely, pretreatment with KYN, atropine or Nic within the RVLM partially blocked the hyperpiesia and tachycardia evoked by intra-RVLM salusin-β (P<0.05).3. The distribution of salusin-βin tissues and serum levels:It showed that salusin-β endogenously generated in rat tissues including spleen, stomach, small intestine, hypothalamus and serum. The content of salusin-β in spleen was higher than that in other tissues (P<0.05). The content of salusin-β in the spleen, stomach, small intestine together with the serum level of salusin-P increased significantly at 6h after CLP compared with the control group (P<0.05). The content of salusin-β in spleen and serum peaked at 12h, small intestine reached the summit at 24h. While, no significant fluctuations of salusin-β content were observed in stomach. The content of salusin-β in hypothalamus began to increase at 6h, and significantly increase appeared 12h after CLP (P<0.05).Conclusion1. Salusin-β in RVLM can cause dose-dependant elevation of BP and HR.2. Hypertension and tachycardia induced by microinjection of salusin-β into the RVLM is partly mediated by L-type calcium channels, glutamate receptors and muscarinic receptors.3. Salusin-β is endogenously generated in sham operation rats, and the salusin-β content in spleen is higher than that in other tissues. The salusin-β content in sepsis rats is higher than in normal level, and the time-dependent alters of salusin-β in sepsis rats suggests that salusin-β might be involved into the pathogenesis of sepsis.