Sustained Stimulus Paradigms and Sexual Dimorphism of the Aortic Baroreflex in Rat

Abstract

The neurophysiological pathways associated with beat-to-beat regulation of mean arterial pressure are well known. Less known are the control dynamics associated with short term maintained of arterial blood pressure about a homeostatic set point. The barorefex (BRx), the most rapid and robust of neural refexes within the autonomic nervous system, is a negative feedback controller that monitors and regulates heart rate and blood pressure. By leveraging the parasympathetic and sympathetic divisions of the autonomic nervous system, the BRx can change blood pressure within a single heart beat. To better understand these controller dynamics, a classic BRx refexogenic experimental preparation was carried out. This thesis recon rmed previous observations of an electrically-evoked sexually-dimorphic peak depressor response in the BRx of Sprague-Dawley rats and veri ed that these functional refexogenic differences carry over to sustained electrical paradigms. Further, it uncovered interesting recovery dynamics in both blood pressure and heart rate. The rat aortic depressor nerve was used as an experimental target for electrical activation of the parasympathetic-mediated reduction in mean arterial pressure. The duration, frequency, and patterning of stimulation were explored, with emphasis on differences between sexes. By measuring the normalized percent decrease in mean arterial pressure as well as the differences in beats per minute during rest and during stimulation, the null hypothesis was rejected.