Cardiovascular Effects of Acute and Chronic Stimulations of the Hypothalamic Defence Area in the Rat

Abstract

In experiments on rats long‐term intermittent stimulations of the hypothalamic defence area have been performed after that the characteristic responses to such stimulations had been explored in acute experiments. Weak topical stimulations of the defence area in rats induced an alerting response which was regularly accompanied by blood pressure and heart rate increases, increased muscle blood flow and decreased renal and gastrointestinal blood flows. When such weak intermittent stimulations of the hypothalamic defence area were continued for 12 hours daily during about four months the ‘resting’ blood pressure of a stimulated group of rats gradually rose, to become significantly different from that of a control group, which had been identically treated in all respects with exception of the intermittent hypothalamic stimulations. On the basis of these results it is discussed whether episodes of mental stress, which are often repeated during prolonged periods of time and which normally seem to excite the hypothalamic defence area, may act as an efficient “trigger” mechanism for gradually inducing a stage of chronic hypertension.