Increased sympathetic drive during the onset of hypertension in conscious Cyp1a1-Ren2 rats

Despite advances in our understanding concerning the pathology of hypertension, the mechanisms that underpin the origin of hypertension remain to be fully elucidated. This enigma is, at least in part, due to inherent limitations of various animal models of hypertension. Here, we show the genetically modified Cyp1a1-Ren2 rat model, in which the onset and severity of angiotensin II-dependent hypertension can be tightly controlled, as an effective model for investigating increased sympathetic drive for the onset of hypertension. Cyp1a1-Ren2 rats were surgically prepared with radiotelemetric transmitters for the continuous measurement of arterial blood pressure (ABP). ABP was recorded in freely moving rats that were fed with either normal rat chow or a diet containing indole-3-carbinol (0.225% w/w) for 7 days to induce hypertension. Structural morphology of and endothelial NO synthase (eNOS) protein expression in heart and/or vascular tissue were analyzed. Sympathetic tone was estimated using spectral analysis of heart rate variability. The progressive induction of hypertension over 7 days was matched with a parallel increase in sympathetic tone. By day 7 of hypertension, eNOS expression in the mesenteric artery was elevated. However, the elevated ABP, sympathetic tone, and eNOS had not elicited gross morphological remodeling of the heart or vasculature. Importantly, both the increase in sympathetic tone and overexpression of eNOS within the vasculature were reversed when ABP was returned to normal. We conclude that the Cyp1a1-Ren2 rat provides an effective model for investigating specific adverse and transient changes in central sympathetic modulation of arterial blood pressure during the early onset of angiotensin-dependent hypertension.