Upregulation of imidazoline receptors in the medulla oblongata accounts for the enhanced hypotensive effect of clonidine in aortic barodenervated rats

Brain Research
M M El-Mas, Abdel A Abdel-Rahman

Abstract

The present study tested the hypothesis that an upregulation of the imidazoline receptor in the rostral ventrolateral medulla (RVLM) of aortic barodenervated (ABD) rats may account for the enhanced hypotensive effect of clonidine. In vitro autoradiographic radioligand binding studies were utilized to investigate the binding characteristics of imidazoline receptors in the RVLM and nucleus tractus solitarius (NTS), areas that play critical roles in cardiovascular regulation and elicitation of clonidine responses. ABD but not sham operation (SO) caused immediate and significant (P < 0.05) increases in mean arterial pressure (MAP) and heart rate (HR) and an impairment of the baroreflex-mediated HR response (baroreflex sensitivity, BRS). Two days after ABD, these parameters, except BRS, subsided to near-control (SO) levels. Intracisternal (i.c.) administration of clonidine (0.1 micrograms) elicited a 3-fold greater decrease in BP of conscious ABD compared with SO rats (-20.3 +/- 2.6 vs. -7.4 +/- 0.9 mmHg) thus demonstrating the ability of ABD to enhance centrally-mediated hypotensive responses. Autoradiographic visualization of brain sections obtained from separate groups of ABD and SO rats 48 h after surgery preincubated with [3H]i...Continue Reading

Citations

Apr 6, 2006·The Journal of Pharmacology and Experimental Therapeutics·Noha Nassar, Abdel A Abdel-Rahman
Nov 29, 2014·Naunyn-Schmiedeberg's Archives of Pharmacology·Hanan M El-Gowelli, Mahmoud M El-Mas
Dec 22, 2015·Naunyn-Schmiedeberg's Archives of Pharmacology·Marwa Y SallamMahmoud M El-Mas
Jul 23, 1999·Annals of the New York Academy of Sciences·P Ernsberger
Apr 9, 2004·Journal of Cardiovascular Pharmacology·Mahmoud M El-Mas, Abdel A Abdel-Rahman

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