Social stress increases blood pressure and cardiovascular pathology in a normotensive rat model

Territorial stress (TS) elevates blood pressure (BP) in several mammalian species. However, cardiovascular pathology following chronic stress has not been consistently shown in a non-genetic hypertension model. Therefore, the hypothesis tested was that social stress would directly increase: BP, collagen deposition in coronary and mesenteric arteries, and myocardial fibrosis. Wistar-Kyoto (WKY) male rats, four weeks of age, were divided into one of three groups: controls (n = 9), territorial stress (TS, n = 12), and social isolation followed by territorial stress (SITS, n = 11). Blood pressure was measured biweekly, and blood samples biweekly for serum testosterone, corticosterone, epinephrine and norepinephrine. Blood pressure significantly increased in the TS (130 mmHg, p < 0.05) and SITS (150 mmHg, p < 0.05) groups, compared to controls (120 mmHg, ANOVA, F = 6.7, p < 0.001). Coronary collagen was increased 47% in the TS group and 90% in the SITS group compared to controls (p < 0.05). The coronary wall/lumen ratio increased significantly (45%, p < 0.05) in the SITS group compared to the controls. Myocardial fibrosis was increased 27% in the TS group and 74% in the SITS group compared to controls (p < 0.05). In conclusion, stress treatments increased BP and cardiac pathology in a normotensive rat strain.