The role of the baroreceptor reflex during hypertension is controversial. The proposed research will focus on three aspects of baroreflex function in hypertension: changes in receptor function in hypertension, baroreflex control in vasoactive hormone release in normo- and hypertension, and carotid sinus reflex control of vascular resistance and capacity functions in hypertension. The studies will be performed in hypertensive dogs with chronically isolated carotid sinus regions. Results from hypertensive dogs will be compared to normotensive controls. The possibility will be examined that a reduced compliance of the carotid sinus itself could contribute to a loss of functional baroreflex control in hypertension. The ability of the baroreflex to adapt to rapid changes in prevailing pressure, the rapid resetting process will be evaluated in hypertensive chronic dogs. The hypothesis will be tested that the changes in baroreflex function seen are occurring at the level of the receptor; measurement of afferent carotid sinus nerve activity will be used to assess changes in receptor-nerve characteristics. Inhibition of the carotid sinus by the action of the contralateral sinus will be assessed in hypertension. Carotid baroreflex release of vasoactive hormones will be studied in normo- and hypertensive dogs. The hypothesis to be tested is that increased release of these vasoactive hormones known to be released during physiological stresses contributes to the maintenance of elevated pressure levels in hypertension. Hormones to be studied include vasopressin, nor-epinephrine and B-endorphin. Baroreflex control of systemic vascular resistance will be examined. The entire systemic pressure-flow relationship will be measured and compared acutely in hypertensive dogs on cardiac bypass. In a further series of experiments, carotid baroreflex control of systemic vascular compliances will be measured. The hypothesis to be tested is that reduced vascular compliances and diminished reflex changes in compliance can account for the altered arterial pressure regulation in hypertension. In another series of proposed experiments, carotid sinus reflex control of systemic vascular capacity, and particularly unstressed vascular volume, will be assessed in hypertensive dogs on cardiac bypass. The final experiment will assess, both chronically and acutely, the differential changes in regional vascular resistance and capacity in hypertension. These experiments will provide new and important information regarding the mechanisms of afferent and efferent baroreflex control during hypertension.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29HL038316-04
Application #
3471098
Study Section
Cardiovascular and Renal Study Section (CVB)
Project Start
1988-04-01
Project End
1993-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
4
Fiscal Year
1991
Total Cost
Indirect Cost
Name
University of Maryland Baltimore
Department
Type
Schools of Dentistry
DUNS #
003255213
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Wolfer, R S; Lovell, N H; Brunner, M J (1994) Exogenous arginine vasopressin does not enhance carotid baroreflex control in the conscious dog. Am J Physiol 266:R1510-6
Wolfer, R S; Bishop, G G; Burdett, M G et al. (1994) Extravascular fluid uptake during cardiopulmonary bypass in hypertensive dogs. Ann Thorac Surg 57:974-80
Brunner, M J; Bishop, G G; Shigemi, K (1993) Arterial compliance and its control by the baroreflex in hypertensive dogs. Am J Physiol 265:H616-20
Brunner, M J; Bishop, G G; Shigemi, K et al. (1993) Arterial pressure-flow relationships in hypertensive dogs: effect of carotid sinus baroreflex. Am J Physiol 265:H986-92
Bishop, G G; Shigemi, K; Freeman, J P et al. (1993) Baroreflex control of arterial and venous compliances and vascular capacity in hypertensive dogs. Am J Physiol 265:H96-102
Geerdes, B P; Frederick, K L; Brunner, M J (1993) Carotid baroreflex control during hemorrhage in conscious and anesthetized dogs. Am J Physiol 265:R195-202
Brunner, M J; Kligman, M D (1993) Hemodynamic and respiratory responses to carotid sinus pressure alteration in experimental hypertension. J Appl Physiol 74:1274-9
Brunner, M J; Kligman, M D (1992) Rapid resetting of baroreflexes in hypertensive dogs. Am J Physiol 262:H1508-14
Carlson, D E; Brunner, M J; Gann, D S (1991) Carotid baroreceptor control of right atrial mechanics in dogs. Am J Physiol 261:H1903-12
Brunner, M J (1991) Carotid sinus compliance and baroreflex responses in hypertensive dogs. Am J Hypertens 4:688-93

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