ROLES OF THE PONTINE PNEUMOTAXIC AND MICTURITION CENTERS IN RESPIRATORY INHIBITION DURING BLADDER CONTRACTIONS

In decerebrate or anesthetized cats with moderately distended urinary bladders, spontaneous bladder contractions (SBCs) have been shown to d ecrease phrenic and hypoglossal nerve activities. To determine the inv olvement of both the pontine micturition center (PMC) and the pneumota xic center in the respiratory response to SBCs, we recorded phrenic an d hypoglossal nerve activities in decerebrate, paralyzed, vagotomized, artificially ventilated cats. Electrical stimulation of the PMC in ca ts with subthreshold bladder volumes below the threshold for SBCs elic ited both increases in intravesical pressure (IVP) and attenuation of respiratory motor nerve activities. Respiration was not altered after PMC lesions, which abolished SBCs, contractions in response to PMC sti mulation, and respiratory inhibition due to passive bladder distension . Electrical stimulation of the pneumotaxic center altered respiratory motor nerve activities and increased IVP in cats with subthreshold bl adder volumes. Pneumotaxic center lesions caused apneusis, but did not abolish the SBCs, which continued to attenuate the apneustic respirat ory motor nerve activity. These results indicate that the PMC is an im portant component of the reflex pathway from urinary bladder distensio n to respiratory inhibition, whereas the pneumotaxic center does not a ppear to be an essential part of this pathway. (C) 1997 Elsevier Scien ce B.V.