Pathophysiological changes associated with stress-induced hypertension in the borderline hypertensive rat

1. This study sought to develop an animal model which would be prone to stress-induced hypertension without spontaneously developing it. 2. Eighteen male rats, F1 offspring of spontaneously hypertensive x Wistar-Kyoto rats, had tail-cuff systolic blood pressures of 152 mmHg at 12 weeks of age. Animals were randomly assigned to three groups of six each: experimental (subjected to 'conflict' 2 h daily for 12 weeks), restraint control (placed in conditioning cages but not subjected to conflict) and maturation control (neither restrained nor stressed). 3. Systolic blood pressure rose significantly in experimental animals to 186 mmHg. Experimental animals studied for a 10 week follow-up period without conflict maintained the elevated pressure. In addition, these animals showed myofibrillar degeneration and an elevation in heart weight/body weight ratios. Restraint animals showed a modest elevation in pressure during the study, but not during the 10 week follow-up. Maturation animals showed no changes in blood pressure. 4. The development of a model of hypertension combining genetics with psychological stress may serve as a means for determining the factors involved in triggering and sustaining stress-induced hypertension which may prove relevant to essential hypertension in man.