Cardiovascular, renal, and neuroendocrine responses to behavioral stress and increased dietary sodium in the borderline hypertensive rat

Author

Brian John Sanders

Date of Award

6-1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Psychology

Major Professor

James E. Lawler

Committee Members

Maureen Groer, William Calhoun, Kathleen Lawler

Abstract

The first filial (F₁ offspring of female spontaneously hypertensive rats (SHR) and male Wistar-Kyoto (WKY) normotensive rats has been shown to develop borderline hypertension (systolic blood pressure = 150 mmHg) in the absence of any environmental manipulation. It has therefore been called the borderline hypertensive rat (BHR). However, when exposed to psychological stress in the form of a shock-shock conflict paradigm or when placed on a high sodium diet the BHR develops severe hypertension (systolic blood pressure = 185 mmHg).

The present study sought to characterize the cardiovascular and renal responses of WKY and BHR during behavioral stress and to determine the influence that a high sodium diet exerts upon these responses.

The study utilized male WKY and BHR rats 8-16 weeks of age. Half of the subjects from each strain were placed on a high sodium diet for eight weeks while the other half remained on a normal diet. During the eighth week of being on their respective diets, all animals were exposed to five days of classical conditioning and were instrumented with chronic bladder, arterial and venous catheters. Cardiovascular measurements and renal function assessments were made on conscious animals during a control period and during one hour (40 trials) of classical conditioning. Blood samples were taken at the end of each recording session for the determinization of plasma catecholamine levels.

The combination of increased dietary sodium and behavioral stress produced no greater degree of hypertension in the BHR than exposure to each stressor separately. Hence, the cardiovascular reactivity of BHR on high sodium was much less than normal sodium controls during stress. With respect to WKY, a high sodium diet did not produce hypertension, but this treatment did prevent the adaptation of blood pressure across trial blocks of stress that was observed in WKY on a normal diet. Furthermore, WKY on a high sodium diet displayed a lack of reactivity to the tone on period during classical conditioning compared to other experimental groups. Finally, the plasma catecholamine data suggest that a high sodium diet reduces sympathetic nervous system functioning in WKY compared to BHR.

The renal function data suggest that the physiological stress of increased dietary sodium and classical conditioning interact in the BHR to decrease renal plasma flow and sodium excretion slightly. Data are discussed in terms of the responses of the BHR's hypertensive parent and the potential ability for the interaction of sodium, stress, and genetics to exacerbate the development of hypertension in the BHR.

Recommended Citation

Sanders, Brian John, "Cardiovascular, renal, and neuroendocrine responses to behavioral stress and increased dietary sodium in the borderline hypertensive rat. " PhD diss., University of Tennessee, 1986.
https://trace.tennessee.edu/utk_graddiss/12468