Repeated Restraint Stress Increases Baseline Blood Pressure in Spontaneously Hypertensive Rats

Abstract

Chronic moderate stress contributes to hypertension in susceptible humans, but this has proven difficult to model in animals. Spontaneously hypertensive rats (SHR) become hypertensive with age and have exaggerated responses to psychological stress. We hypothesized that SHR would be susceptible to chronic moderate stress‐induced hypertension. Arterial pressure was measured by radiotelemetry in control (n=8) and chronically stressed (1hr restraint stress per day during the light period, 6 days a week for 4 wks, n=8) SHR. The average increases in mean arterial pressure (MAP) during restraint was not significantly different (P=0.09) on the first (35±3 mmHg) and final days (32±3) mmHg of restraint. Baseline MAP during the dark period, not directly influenced by stress responses, was elevated in both control and stressed rats with time, but the increase was significantly greater (P<0.05) in the stressed (12±2 mmHg) compared with the unstressed (4±1 mmHg p<0.05) rats. In contrast, nighttime heart rate was not affected by chronic stress. Parallel with the elevation in MAP, preliminary data indicate that microglia activation within the paraventricular nucleus of the hypothalamus increased significantly in stressed rats, suggesting involvement of neuroimmune mechanisms in stress‐induced hypertension. Supported by NIH #HL93186 (MPI)