Failure of Psychosocial Stress to Induce Chronic Hypertension in the Rat

The effect of psychosocial stress produced by aggregation in a special cage designed by Henry was investigated in three separate experiments using Wistar-Kyoto (WKY), Sprague-Dawley (SD) and F1 hybrids of the Japanese spontaneously hypertensive and Wistar-Kyoto (SHR-WKY F1) rats. Each aggregated group displayed typical 'stressed' behavioural disturbances. Adrenal hypertrophy, elevation of plasma renin activity and gastric erosions were noted in male aggregated SD rats; while adrenal enlargement, elevation of plasma noradrenaline and gastric erosions were found in male aggregated SHR-WKY F1 rats. Sustained hypertension, however, did not develop in any strain nor in any subgroup within each strain. Gastric erosions were also noted in isolated SD and SHR-SKY F1 rats suggesting that long term isolation of rats also induces stress. Isolated rats also remained normotensive throughout. Reduced haematocrit was found in both aggregated and isolated male SHR-WKY F1 rats suggesting increased plasma volume. We conclude that neither stress due to psychosocial disturbances nor that due to isolation produces chronic hypertension in the three strains of rat studied.