Journal Article

Low dose of moxonidine within the rostral rentrolateral medulla improves the baroreflex ;ensitivity control of sympathetic activity in hypertensive rat

Jia-ling WANG Long WANG Zhao-tang WU Wen-jun YUAN Ding-feng SU Xin NI Jian-jun YAN Wei-zhong WANG

2009

Overview

Aim： To determine the effects of the centrally antihypertensive drug moxonidine injected into the rostral ventrolateral medulla （RVLM） on baroreflex function in spontaneously hypertensive rats （SHR）. Methods： Baroreflex sensitivity control of renal sympathetic nerve activity （RSNA） and barosensitivity of the RVLM presympathetic neurons were determined following application of different doses of moxonidine within the RVLM. Results： Three doses （0.05, 0.5, and 5 nmol in 50 nL） of moxonidine injected bilaterally into the RVLM dose-dependently reduced the baseline blood pressure （BP） and RSNA in SHR. At the highest dose （5 nmol） of moxonidine injection, the maximum gain （1.24%±0.04%/mmHg） of baroreflex control of RSNA was significantly decreased, However, the lower doses （0.05 and 0.5 nmol） of moxonidine injection into the RVLM significantly enhanced the baroreflex gain （2.34%±0.08% and 2.01%±0.07%/mmHg）. The moxonidine-induced enhancement in baroreflex function was completely prevented by the imidazoline receptor antagonist efaroxan but not by the α2-adrenoceptor antagonist yohimbine. A total of 48 presympathetic neurons were recorded extracellularly in the RVLM of SHR. Iontophoresis of applied moxonidine （30-60 nA） dose-dependently decreased the discharge of RVLM presympathetic neurons but also significantly increased the barosensitivity of RVLM presympathetic neurons. Conclusion： These data demonstrate that a low dose of moxonidine within the RVLM has a beneficial effect on improving the baroreflex function in SHR via an imidazoline receptor-dependent mechanism.

• Subject: 交感神经元 / 低剂量 / 压力感受器反射 / 延髓腹外侧 / 活性控制 / 肾交感神经活动 / 自发性高血压大鼠