The differential effects of imidazoline‐like drugs on the components of baroreflex function in the nucleus of the solitary tract in anesthetized rats

Abstract

Imidazoline‐like drugs (clonidine and moxonidine), agonists of I1‐imidazoline receptor (I1R) and/or α2‐adrenoceptors (α2AR), has been suggested to produce the cardiovascular inhibition in the central nervous system, which is associated with baroreflex modulation. The nucleus of the solitary tract (NTS) is a crucial region involved in cardiovascular and baroreflex regulation. This study was to comparatively detect the effects of clonidine and moxonidine on the baroreflex control of heart rate (HR) or renal sympathetic nerve activity (RSNA) in normotensive rats. In urethane and α‐chloralose anesthetized rats, bilateral microinjection of clonidine (2 nmol), a mixed agonist of I1R and α2AR, into the NTS increased the baroreflex control of HR (1.13 ± 0.1 vs. 1.79 ± 0.2 bpm/mmHg, P<0.05) and RSNA (1.19 ± 0.2 vs. 1.73 ± 0.3 %/mmHg, P<0.05). Bilateral NTS injection of the selective I1R agonist moxonidine (4 nmol) increased the baroreflex control of RSNA (1.22 ± 0.2 vs. 1.79 ± 0.3 %/mmHg, P<0.05) without affecting the baroreflex control of HR (1.15 ± 0.1 vs. 1.18 ± 0.2 bpm/mmHg, P>0.05). In conclusion, the present results demonstrate that the imidazoline‐like drug clonidine and moxonidine in the NTS differentially modulate the baroreflex components, which probably is dependent on acting receptors. (Supported by the National Natural Science Foundation of China, No. 30470636 and 30670759)