THE EFFECTS OF CHEMICAL STIMULATIONS OF THE PONTINE MICTURITION CENTER IN DECEREBRATE CATS

Abstract

In acute decerebrate cats, the pontine micturition center (PMC) was identified by electrical microstimulation, and then putative chemical transmitter agents such as carbachol, acetylcholine, noradrenaline and enkephalin were microinjected into it. The effects of each agent upon micturition reflex were studied. When the bladder was filled with subcritical volume of physiological saline, carbachol (10mM or 100mM, 0.1μl) and acetylcholine (100mM, 0.1μl) microinjections into the PMC resulted in micturition. The pattern of changes in bladder pressure and the external urethral sphincter muscle activity was almost identical to those observed during reflex micturition and electrically induced micturition. Upon reflex micturition, carbachol, acetylcholine and noradrenaline microinjections into the PMC resulted in an increase in the maximum bladder pressure and a decrease in bladder capacity, while enkephalin microinjections resulted in a decrease in the maximum bladder pressure and an increase in the bladder capacity. These results indicate that, for the neurons of the PMC, cholinergic inputs act as micturition executing ones, while noradrenergic and enkephalinergic inputs act as micturition modifying ones, exerting facilitatory and inhibitory effects to the PMC, respectively.