Modulation of respiratory motor output during micturition is dependent on level of respiratory drive

Abstract

The goal of this study was to examine the interaction between micturition reflexes and respiratory motor output in rats. To this end, phrenic nerve, abdominal muscle, and external urethral sphincter activity were recorded in urethane‐anesthetized, vagotomized, ventilated adult female Sprague‐Dawley rats during passive bladder filling and spontaneous bladder contractions (voiding) elicited by infusion of physiological saline into the bladder. Respiratory drive was controlled by altering ventilation rate and monitored through blood gases. Phrenic and abdominal activities were both influenced by micturition particularly during and after active bladder contraction. Specifically, at low to medium levels of respiratory drive (i.e., close to apneic threshold) the amplitude and frequency of phrenic bursts transiently decreased immediately following bladder contraction. At high levels of respiratory drive phrenic bursts were largely unaffected by bladder contraction whereas abdominal muscles were activated exhibiting tonic activity during and phasic (expiratory) activity following bladder contraction. Thus, multiple respiratory motor outputs are modulated during micturition and the degree of modulation is sensitive to the level of respiratory drive. Supported by HL63175 and NS049310.