Ca2+ signalling in urethral interstitial cells of Cajal

Interstitial cells of Cajal (ICC) in the urethra have been proposed as specialized pacemakers that are involved in the generation of urethral tone and therefore the maintenance of urinary continence. Recent studies on freshly dispersed ICC from the urethra of rabbits have demonstrated that pacemaker activity in urethra ICC is characterized by spontaneous transient depolarizations (STDs) under current clamp and spontaneous transient inward currents (STICs) under voltage clamp. When these events were simultaneously recorded with changes in intracellular Ca2+ (using a Nipkow spinning disk confocal microscope) they were found to be associated with global Ca2+ oscillations. In this short review we will consider some of these recent findings regarding the contribution of intracellular Ca2+ stores and Ca2+ influx to the generation of pacemaker activity in urethral ICC with particular emphasis on the contribution of reverse Na+/Ca2+ exchange (NCX).