Excessive salt-ingestion in man has long been associated with an increased risk of developing hypertension, yet the mechanisms by which salt acts are poorly understood. In the Dahl rat model, Salt-Sensitive rats (DS) develop elevated blood pressures on a high salt (HS) diet while Salt-Resistant rats (DR) remain normotensive. Recent research has suggested that there is a significant neurogenic contribution to the development of hypertension in DS rats. The arterial and cardiopulmonary baroreflexes of DS rats are depressed even before exposure to high salt and the subsequent development of hypertension. This project will test whether abnormal function of the cardiovascular mechanoreceptors contributes to these decreases in baroreflex sensitivity in DS rats. I will use two in vitro preparations to study quantitatively the response characteristics of aortic arch baroreceptors and cardiopulmonary mechanoreceptors located in the superior vena cava just outside the right atrium. This in vitro approach allows a much more precise control of experimental conditions including reproducible, well-defined pressure inputs and ionic environment. In addition, the geometry of the vessel walls in which these mechanoreceptors are found can be closely approximated by a simple right cylinder so that the contribution of vessel wall distensibility and mechanics can be assessed through measurements of vessel diameter. Single mechanoreceptors will be tested for steady-state discharge characteristics including threshold and suprathreshold sensitivity, for rapid resetting to changes in the conditioning pressure and for sensitivity to changes in external ionic concentrations. Of particular importance are the comparisons of an inbred, nonselected strain of control rats (Sprague-Dawley) to both DS and DR and the effect of low salt and high salt diets.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL033436-02
Application #
3345341
Study Section
Experimental Cardiovascular Sciences Study Section (ECS)
Project Start
1985-07-01
Project End
1988-06-30
Budget Start
1986-07-01
Budget End
1987-06-30
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Andresen, M C; Yang, M (1992) Smooth muscle tone and rapid resetting of rat aortic baroreceptors. Circ Res 70:116-22
Andresen, M C; Yang, M (1992) Gadolinium and mechanotransduction of rat aortic baroreceptors. Am J Physiol 262:H1415-21
Yang, M Y; Andresen, M C (1991) Rapid baroreceptor resetting in Dahl salt-sensitive rats. Hypertension 17:541-5
Andresen, M C; Yang, M Y (1990) Dynamic and static conditioning pressures evoke equivalent rapid resetting in rat aortic baroreceptors. Circ Res 67:303-11
Yang, M Y; Andresen, M C (1990) Peptidergic modulation of mechanotransduction in rat arterial baroreceptors. Circ Res 66:804-13
Andresen, M C; Yang, M; Nelson, S H et al. (1990) Cocaine inhibits baroreflex control of blood pressure by actions at arterial baroreceptors. Am J Physiol 258:H1244-9
Andresen, M C; Rudis, S K; Bee, D E (1989) Aberrant baroreceptor mechanotransduction in adult Dahl rats on low-salt diet. Am J Physiol 256:H446-54
Andresen, M C; Yang, M (1989) Interaction among unitary spike trains: implications for whole nerve measurements. Am J Physiol 256:R997-1004
Andresen, M C; Yang, M (1989) Arterial baroreceptor resetting: contributions of chronic and acute processes. Clin Exp Pharmacol Physiol Suppl 15:19-30
Andresen, M C; Yang, M Y (1989) Rapid baroreceptor resetting is unaltered by chronic hypertension in rats. Am J Physiol 256:H1228-35

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