Mechanisms mediating NTS P2x receptor-evoked hypotension: cardiac output vs. total peripheral resistance

diac output vs. total peripheral resistance. Am J Physiol Heart Circ Physiol 281: H2198–H2203, 2001.—We have pre-viously shown that P2x purinoceptor activation in the sub-postremal nucleus tractus solitarius (NTS) produces dose-dependent decreases in mean arterial pressure (MAP), heart rate, efferent sympathetic nerve activity, and significant pe-ripheral vasodilation. However, the relative roles of cardiac output (CO) and total peripheral resistance (TPR) in medi-ating this depressor response are unknown. Bradycardia does not necessarily result in decreased CO, because, with the greater filling time, stroke volume may increase such that CO may be unchanged. We measured changes in CO (via a chronically implanted flow probe on the ascending aorta) and MAP in a-chloralose- and urethane-anesthetized male Sprague-Dawley rats in response to microinjection of th