<b>Urothelium could be important for vesical pain </b>

Abstract

Urothelium has been a new key for vesical pain and/or the unusual sensation form the urinary bladder. Afferent fibers in the smooth muscle are mostly A delta fibers and sensitive to distention of the urinary bladder, In contrast, C-fibers in the pelvic afferent fibers were called as “silent fibers”, since the functional significance during the normal micturition was not clear. Recent histological study demonstrated unmyelinated fibers were located submucosal area and urothelium. These contained CGRP and/or substance P. TRPV1 channel in the urothelium released ATP, and P2X3 receptors in the afferent nerve terminals elicited the neural activities. Alpha-1D receptors were also in the urothelium and released ATP. Acetylcholine receptors (M2 and M3 and nicotinic receptors) presented in the urothelium. Acetylcholine was also released from the urothelium. During the inflammation of the urinary bladder, prostaglandin E2 in the urine was increased. EP1 receptors, prostaglandin receptors, presented in the urothelium and primary afferent nerve terminals. These also increased the afferent activity. Variety of neurotransmitter receptors and channels in the urothelium releasing ATP and acetylcholine should be important for controlling the micturition reflex in the pathological condition including the visceral pain.