Response of the canine bladder base during reflex micturition

The response of the bladder base to filling and voiding was studied in a surgical dog model in which the bladder base was separated from the main body and closed to form a chamber. In the bladder distension phase there was a reduction in pressure in the bladder base chamber, which implies relaxation of the bladder base. In the expulsion phase the reflex bladder body activity took place with an increase in bladder base pressure, indicating contraction. Relaxation and contraction were blocked by propranolol and phentolamine respectively and both responses were abolished by trimetaphan. It was concluded that the bladder base activity in the micturition cycle is a reflex action mediated via the sympathetic nervous system.