Comparison of the pharmacological and sequence methods for assessing baroreflex control blood pressure via heart rate and renal sympathetic nerve activity

Abstract

In many cardiovascular diseases, the sensitivity of the baroreflex is impaired. To determine baroreflex sensitivity in the laboratory, we have traditionally infused vasoactive drugs to alter blood pressure and recorded the responses of renal sympathetic nerve activity and heart rate. However, the pharmacological method is not always practical and thus there is a shift to obtaining baroreflex response curves from naturally occurring fluctuations in arterial pressure. The aim of this project was to establish the practicalities of using spontaneous fluctuations in arterial pressure to determine the sensitivity of the baroreflex in conscious unrestrained animals and make comparisons to traditional pharmacological methods. Gains of the baroreflex control of heart rate were comparable between the two methods but spontaneous baroreflex gains for the baroreflex control for sympathetic nerve activity were greater than those obtained from pharmacological methods. It must also be noted that the sequence methods only provides gain measurements and no information on the operating range of the reflex. Supported by the Health Research Council of New Zealand and University of Auckland Research Committee.