Bladder contractions alter inspiratory termination by superior laryngeal and intercostal nerve stimulation

Gradual distension of the urinary bladder evokes spontaneous bladder contra ctions (SBCs), which are associated with reduced inspiratory activity in th e phrenic and other inspiratory motor nerves. We examined the influence of isovolumetric SBCs on the threshold for termination of phrenic inspiration by electrical stimulation of superior laryngeal and/or mid-thoracic interco stal nerves (ICN) in decerebrate, vagotomized, paralyzed, ventilated cats. Although SBCs reduced phrenic inspiratory activity, the threshold for inspi ratory termination by nerve stimulation was increased. The results emphasiz e the complexity of the synaptic connections among brain stem neurons gover ning micturition and breathing. (C) 1999 Elsevier Science B.V. All rights r eserved.