• urethra;
  • smooth Muscle;
  • pacemaker;
  • interstitial cells of Cajal;
  • Calcium oscillations


The smooth muscle layer of the urethra generates spontaneous mayogenic tone that is thougth to make a major contibution to urinary continence. The mechanisms underlying generion of tone remin unclear, however recent studies from our laboratory highlighted a role for a specialised population of pacemake cells which we originally referrd ot as interstitil cells (IC) and now term ICC. Urethra ICC possess an electrical pacemaker mechanism charactriesd by rhythmic activation of Ca2+-activated C1- Channels leading to spotaneous transient inward currents (STICs) under voltage clamp and spontaneous transient deplarisations (STDs) under surrent clamp conditons. Both STICS and STDs are now known to be associated with spntaneous Ca2+ under current clamp conditons. Both STIC and STDs are now known to be associated with spontaneius Ca2+ oscillations that result from a complex interplay between releas fo Ca2+ from intracellular stores and Ca2+ influx acrosss the plasma membrane. Ink this review we will consider some of the precise mechanisms involved in the generation of paccemake activity and discuss how these are modulated by excitatory and inhibitory neurotrnsmiters.