[Enkephalinergic receptors at the level of the lower urinary tract]

After describing the autonomic nervous system of the lower urinary tract and its neurotransmitters, the authors discuss the recent discovery of new endomorphine group mediators--the enkephalins. There exist enkephalin immunoreactive nerve fibers in the smooth muscles of the bladder and the prostate. This neuromediator is synthetized in the spinal cord in the body of the preganglionic neuron and is carried by the axon flow towards the intramural parasympathetic ganglions of the bladder. The physiological effects of enkephalins are similar to those of morphinics and are antagonized by naloxone. Enkephalins inhibit spontaneous or provoked contractions of the bladder by inhibiting action on the parasympathetic neurons. This property of relaxing the muscles of the bladder, in both volume and pressure, may open up new vistas for uropharmacological research.