Facilitation of reflex bradycardia does not contribute to the enhanced hypotensive effect of clonidine in aortic barodenervated rats

Journal of Cardiovascular Pharmacology
M M El-Mas

Abstract

Our previous studies showed that the hypotensive effect of clonidine is enhanced in rats with surgically eliminated aortic baroafferents. In this study, we investigated whether this effect of clonidine is related to facilitation of baroreceptor control of reflex bradycardia. The effects of clonidine on blood pressure (BP), heart rate (HR), and baroreflex-mediated decreases in HR (baroreflex sensitivity, BRS) were studied in conscious aortic barodenervated (ABD) and sham-operated (SO) rats. The slope of the baroreflex curve relating increments in mean arterial pressure (MAP) induced by phenylephrine to corresponding baroreflex-mediated bradycardic responses was taken as an index of BRS. ABD but not the sham operation caused immediate and significant (p < 0.05) increases in BP and HR and an impairment of BRS. Two days after ABD, these parameters, except the BRS, subsided to near control levels. Starting from similar baseline values of BP and HR, clonidine (30 microg/kg, i.v.) elicited significantly (p < 0.05) greater decreases in MAP in conscious ABD rats compared with SO rats (-23 +/- 2 mm Hg vs. -7 +/- 2 mm Hg). The enhanced hypotensive effect of clonidine in ABD rats was associated with a significant reduction in baroreceptor-...Continue Reading

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Citations

Mar 17, 2005·Cardiovascular Drugs and Therapy·Amal G Omar, Mahmoud M El-Mas
May 10, 2011·Toxicology and Applied Pharmacology·Mahmoud M El-MasEvan I Saad
May 23, 2012·Food and Chemical Toxicology : an International Journal Published for the British Industrial Biological Research Association·Osama F HarrazMahmoud M El-Mas
Mar 28, 2006·Journal of Pharmacological Sciences·Jin WangDing-Feng Su
Jun 28, 2016·Neuromodulation : Journal of the International Neuromodulation Society·Mortimer GierthmuehlenDennis T T Plachta
Mar 22, 2002·The Journal of Pharmacology and Experimental Therapeutics·Mahmoud M El-MasFouad M Sharabi

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