115 RENAL CIRCULATORY RESPONSES TO ACTIVATION OF SOMATO-SYMPATHETIC AND BARORECEPTOR REFLEXES IN PIGLETS

Abstract

The degree of participation of the renal circulation in neonatal cardiovascular responses was evaluated by altering afferent inputs to the central regulatory system. Thirty-seven piglets from 1-25 days were anesthetized with 0.25-0.5% halothane in N₂0-0₂, paralyzed and artificially ventilated to maintain normal arterial blood gases and pH. Renal arterial flow was recorded continuously (electromagnetic transducer) with aortic pressure (AoP) and heart rate. Resistance (R) was calculated as ≥/mean flow. Baroreceptor stimulation, by sudden high pressure infusion of 1-2ml of saline through a catheter whose tip was located in the carotid sinus, lowered ≥ 11-17% in all piglets; renal R decreased in piglets ≥1 week. Baroreceptor inhibition, by 10-30sec occlusion of both common carotid arteries, elevated ≥ 11-17% in all animals; renal R increased in piglets ≥1 week. Somato-sympathetic reflexes were elicited by stimulation of the central cut end of the right sciatic or median nerve with 10sec trains of 1.0msec pulses over the ranges of 0.2-1.0mA and 1-100Hz. In piglets of all ages, high frequency stimulation increased renal R significantly (at least 19%). The renal vasculature appears to participate at a younger age in integrated cardiovascular responses to somato-sympathetic reflexes than to baroreceptor reflexes. (Supported by Nassau Heart Assoc.)

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