Biomaterial Database

Centrally mediated reduction in cardiac output elicits the enhanced hypotensive effect of clonidine in conscious aortic barodenervated rats. 1994

M M el-Mas, and R G Carroll, and A A Abdel-Rahman

Department of Pharmacology, East Carolina University School of Medicine, Greenville, North Carolina 27858.

In a previous study, we showed that centrally mediated hypotensive responses are enhanced in aortic barodenervated (ABD) rats as compared with sham-operated (SO) rats. In the present study, we tested the hypothesis that the high basal total peripheral resistance (TPR) of ABD rats accounts for enhanced hypotensive responses to clonidine in this rat model. Aortic barodenervation resulted in acute increases in blood pressure (BP) and heart rate (HR) in anesthetized rats, associated with significant increases in plasma norepinephrine (NE) levels and TPR; cardiac index (CI) and stroke volume (SV) were not affected. After recovery from anesthesia, conscious ABD rats had significantly increased BP at 3 h after barodenervation; BP returned to SO levels by 48 h even though plasma NE levels and TPR remained significantly increased. On the other hand, CI and SV showed significant reductions, beginning at 3 h, and remained low throughout the postdenervation period (48 h); the reduction in CI offset the increase in TRP and may therefore account for the restoration of BP of ABD rats to normal levels. Beginning at similar baseline BP values, cumulative intracisternal (i.c.) doses of clonidine (0.02-2.5 micrograms) elicited greater decreases in BP and plasma NE levels in conscious ABD as compared with SO rats. These responses were centrally mediated because systemic administration of 0.12 micrograms clonidine, a dose that elicited near maximal hypotensive response after i.c. administration, affected neither BP nor plasma NE levels. Contrary to the hypothesis, the hypotensive effect of clonidine in ABD rats resulted exclusively from a reduction in CO (owing to reductions in both HR and SV) because TPR was not affected. These findings suggest that (a) in ABD rats, a reduction in CO offsets a sustained sympathetically mediated elevation in TPR and restores BP to normal levels; and (b) an enhanced hypotensive response to clonidine in ABD as compared with SO rats cannot be accounted for by a higher basal TRP but rather by elicitation of greater reductions in CO through a centrally mediated sympathoinhibitory action.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D011311	Pressoreceptors	Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.	Baroreceptors,Receptors, Stretch, Arterial,Receptors, Stretch, Vascular,Stretch Receptors, Arterial,Stretch Receptors, Vascular,Arterial Stretch Receptor,Arterial Stretch Receptors,Baroreceptor,Pressoreceptor,Receptor, Arterial Stretch,Receptor, Vascular Stretch,Receptors, Arterial Stretch,Receptors, Vascular Stretch,Stretch Receptor, Arterial,Stretch Receptor, Vascular,Vascular Stretch Receptor,Vascular Stretch Receptors
D001794	Blood Pressure	PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.	Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D001921	Brain	The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.	Encephalon
D002302	Cardiac Output	The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat).	Cardiac Outputs,Output, Cardiac,Outputs, Cardiac
D002395	Catecholamines	A general class of ortho-dihydroxyphenylalkylamines derived from TYROSINE.	Catecholamine,Sympathin,Sympathins
D003000	Clonidine	An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.	Catapres,Catapresan,Catapressan,Chlophazolin,Clofelin,Clofenil,Clonidine Dihydrochloride,Clonidine Hydrochloride,Clonidine Monohydrobromide,Clonidine Monohydrochloride,Clopheline,Dixarit,Gemiton,Hemiton,Isoglaucon,Klofelin,Klofenil,M-5041T,ST-155,Dihydrochloride, Clonidine,Hydrochloride, Clonidine,M 5041T,M5041T,Monohydrobromide, Clonidine,Monohydrochloride, Clonidine,ST 155,ST155
D003714	Denervation	The resection or removal of the nerve to an organ or part.	Laser Neurectomy,Neurectomy,Peripheral Neurectomy,Radiofrequency Neurotomy,Denervations,Laser Neurectomies,Neurectomies,Neurectomies, Laser,Neurectomies, Peripheral,Neurectomy, Laser,Neurectomy, Peripheral,Neurotomies, Radiofrequency,Neurotomy, Radiofrequency,Peripheral Neurectomies,Radiofrequency Neurotomies
D006339	Heart Rate	The number of times the HEART VENTRICLES contract per unit of time, usually per minute.	Cardiac Rate,Chronotropism, Cardiac,Heart Rate Control,Heartbeat,Pulse Rate,Cardiac Chronotropy,Cardiac Chronotropism,Cardiac Rates,Chronotropy, Cardiac,Control, Heart Rate,Heart Rates,Heartbeats,Pulse Rates,Rate Control, Heart,Rate, Cardiac,Rate, Heart,Rate, Pulse
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia