[Effects of afferent vagal stimulation and distention of the upper digestive tract on the micturition reflex and activity of the pontine micturition center in dogs].
(1) The study was performed to elucidate the effects of afferent vagal stimulation and distension of the digestive tract on the micturition reflex in 21 acute decerebrate dogs immobilized with gallamine. Electrical stimulation of the central cut end of the cervical vagus nerve with high voltage (17.5-25 V) and moderate frequency (10-50 Hz) elicited in most cases inhibition of the periodic bladder contractions and of outflows of the pelvic vesical branch which were induced by a sustained intravesical pressure of 10-15 cmH2O. Distension of the thoracic esophagus, the stomach, and the duodenum also induced inhibition of the bladder contractions and of the pelvic outflow to the bladder. Such inhibitions were abolished after bilateral cervical vagotomies except a few cases of distension of the duodenum. (2) Another series of experiments were undertaken to clear the effect of afferent vagal stimulation on the electrical activity of the pontine micturition center in 10 acute decerebrate dogs. By means of an extracellular glass microelectrode method, unitary discharges synchronized with the grouping discharges in the pelvic vesical branch with a rhythm of 2.2-2.5 Hz were recorded from the pontine micturition center in the dorsolateral pontine tegmentum. Such a type of discharges was detected in 6 of 59 units which discharged by afferent stimulation of the pelvic vesical branch. This type of discharges was inhibited by afferent vagal stimulation at the supradiaphragmatic level. From these results, it may be concluded that the afferent pathway of the bladder relaxation reflex induced by distension of the upper digestive tract is mainly involved in the vagal nerves, but in some cases of the strong distension of the duodenum, the pathway is in splanchnic nerves, and that inhibition of the bladder contraction after stimulation of vagal nerve is induced by suppression of the pontine micturition centers.
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Department of Physiology, Kawasaki Medical School.
D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D003655:Decerebrate State / Q000503:physiopathology; D004068:Digestive System Physiological Phenomena; D004285:Dogs; D004558:Electric Stimulation; D011149:Pons / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D001743:Urinary Bladder / Q000294:innervation / Q000502:physiology*; D014554:Urination / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*