Am~:rican Joijknal of P~iysiology

IAN, Y. C. Autonomic neruous control of cardiovascular response during diving in the rat. Am. J. Physiol. 227(3): 601-605. 1974.-The diving response of the unanesthetized rats was produced by submerging the head up to eye level in 30°C water by head-down tilting. The head-down tilting without head immersion served as the predive control. A steady response of blood pressure (BP) and heart rate (HR) to diving was established within 5 s following head immersion. HR was reduced by 64’;j, and BP increased by 15 y0 during cliving. Sympathetic tone was reduced by 61 y0 and parasympathetic tone increased 306c;I, from the predive values, whereas intrinsic heart rate was not altered during diving, as deduced from selective autonomic blockade by atropine or propranolol. Cardiac output was reduced by 72y0 and total peripheral resistance increased fourfold from the predive values. Stroke volume was not changed, stroke work increased by 24-n/;:, and left ventricular power decreased by 650;; during diving. The unanesthetized rats indicated a diving response qualitatively and quantitatively similar to that of diving mammals rather than nondiving species. It is a potential model for diving studies so far as cardiovascular responses are concerned.