Interaction of thermal and baroreceptor reflexes in man

Abstract

The purpose of the study was to consider a possible central interaction of two cardiovascular reflexes: the thermal reflex and the responses of the baroreceptors to lower body negative pressure (LBNP). Vasoconstrictor responses to LBNP were measured in one finger and forearm during immersion of the other arm in hot, warm, or cold water. Changes in temperature in the vascular beds we were studying were thereby eliminated, allowing examination of the interaction of the reflex effects of thermal and baroreceptor stimuli. In the finger, the response to LBNP was almost abolished during heating and greatly augmented by cooling. In the forearm, the vasoconstrictor response to LBNP tended to be less during heating. The thermal stimuli did not affect responses to norepinephrine, so the effect on reflex responses to LBNP is not the result of altered responses to the neurotransmitter. It is concluded that thermal stimuli modify the baroreceptor reflex and that the interaction of the thermal and baroreceptor reflexes may occur at a central level.