Brain-stem regions for stimulus-bound and stimulus-related respiration

Abstract

Application of periodic bursts of electrical pulses to an extensive region in the brain stem of anesthetized cats can modify the spontaneous respiration so that it becomes phase-locked to the stimulus bursts. This phenomenon is called stimulus-bound respiration rate if the ratio between respiration rate and bursts rate is one; and it is called stimulus-related respiration rate if the ratio is other than one. The part of the brain which elicits this phenomenon extends from the preoptic region to the caudal medulla oblongata. It includes the pneumotaxic, apneustic, and the medullary respiratory centers. In general, stimulus-related respiration can be obtained from a region adjacent to and surrounding that for stimulus-bound respiration responses. From some parts in the reticular formation, stimulus-bound respiration can be evoked without concomitant changes in arterial pressure, heart rate and motor responses. This suggests that these regions deal with the specific function of controlling respiration rate, different from the general function of reticular activation. A tentative hypothesis, with the direct participation of only the medullary respiratory centers, is offered as the underlying neurophysiological mechanism for stimulus-bound respiration.