Autonomic impairment in essential hypertension in rats: representation by a computerized model

Additional insight is provided into autonomic blood pressure control in a normotensive vs. a hypertensive system, focusing on autonomic impairment as reflected in the time dependent heart-rate response to changes in arterial blood pressure (ABP). Three-month old, conscious, spontaneously hypertensive rats (SHR) were compared to their normotensive controls (WKY). In order to cause abrupt changes in ABP, multiple bolus injections of the vasoconstrictor phenylephrine and the vasodilator nitroprusside were administered. A computerized procedure based on peak detection from ABP, was used to obtain heart rate (HR) and mean systolic and diastolic ABP as a function of time after injection. The HR response to ΔABP was observed at baseline as well as under vagal or β-sympathetic blockade. Gain and time delays of the various control limbs were extracted for each strain. Results indicate that WKY are capable to correct more effectively small and medium ABP changes, while SHR display a minimal HR response to small ABP changes but are capable of correcting large ABP increases