Inhibition of rhynchophylline on carotid sinus baroreceptor activity in anesthetized rats / 中国药理学与毒理学杂志

ABSTRACT

AIM To elucidate the effect of rhynchophylline(Rhy) on carotid sinus baroreceptor activity (CBA). METHODS By recording sinus nerve afferent discharge activity with isolated carotid sinus perfusion, parameters of CBA, such as peak slope (PS), peak integral value (PIV), threshold pressure (TP) and saturation pressure (SP) were examined. ①Rhy 10, 50, and 100 μmol·L-1, dissolved in K-H solution, was perfused into isolated carotid sinus, then the effects of Rhy on parameters of CBA were observed while intrasinus pressure was altered in a stepwise manner. ②NG-nitro-L-arginine methyl ester (L-NAME) 10 mmol·L-1, tetraethylammonium (TEA) 1 mmol·L-1 and Bay K8644 500 nmol·L-1 were perfused into isolated carotid sinus, and effects of them on the response of carotid baroreceptor to Rhy were observed. RESULTS ① By perfusing the isolated carotid sinus with Rhy 10 μmol·L-1, PS decreased from (19.2±0.3)% to (18.2±0.1)%·kPa-1and the PIV decreased from (219.3±3.3)% to (199.1±3.8)%, while TP and SP increased from (8.2±0.3) to (9.1±0.1)kPa and (21.5±0.1) to (22.1±0.1)kPa, respectively. By perfusing with Rhy 50 and 100 μmol·L-1, the changes in PS, TP and SP were in concentration-dependent manner, and this indicated inhibitory effect of Rhy on CBA. ②Pretreatment with L-NAME 100 μmol·L-1 did not affect inhibitory action of Rhy 50 μmol·L-1 on CBA. ③Pretreatment with TEA 1 mmol·L-1 had no effect on inhibitory effect of Rhy 50 μmol·L-1 on CBA. ④Pretreatment with Bay K8644 500 nmol·L-1 could mostly attenuate effect of Rhy 50 μmol·L-1 on CBA. CONCLUSION Rhy inhibits CBA via blocking calcium influx in baroreceptor nerve ending.