Effect of Interaction of the Hypothalamus and the Carotid Sinus Mechanoreceptor System on Renal Hemodynamics in the Anesthetized Dog

Abstract

The purpose of this investigation was to show how the operating characteristics of the reflex having carotid sinus pressure as an input and renal pressure and flow as an output are modified by graded stimulation of the posterior hypothalamus. Consequently, the effects of graded stimulation of the posterior hypothalamus on renal hemodynamics were investigated in the anesthetized dog. The carotid sinuses were isolated and subjected to controlled pulsatile pressures. In general, discrete stimulation of the hypothalamus caused a frequency-dependent increase in renal impedance, and stimulation of the carotid sinus caused a decrease. Concomitant stimulation of the hypothalamus and the carotid sinuses had a significant, nonalgebraic effect on the d-c impedance (renal resistance) but no effect on renal impedance at high frequencies. Hypothalamic stimulation modified the sensitivity of renal resistance to carotid sinus pressure. This reflex sensitivity to hypothalamic stimulation passed through a single maximum. The estimated characteristic renal impedance varied inversely with carotid sinus pressure due to active vasomotor changes in renal vascular mechanical properties, rather than to passive effects of concomitant blood pressure changes.