Abstract
The prostate is a gland whose secretions contribute to the seminal fluids ejaculated upon activation of autonomic sympathetic nerves. In elder males, the prostate undergoes an increase in stroma mass and myogenic tone, leading to benign prostatic hyperplasia that occludes the proximal urethra and the presentation of various lower urinary tract symptoms that decrease their quality of life. This review summarises the role of prostatic interstitial cells (PICs) in the generation of the spontaneous tone in the prostate. It presents current knowledge of the role of Ca(2+) plays in PIC pacemaking, as well as the mechanisms by which this spontaneous activity triggers slow wave generation and stromal contraction. PICs display a small T-type Ca(2+) current (I(CaT)) and a large L-type Ca(2+) current (I(CaL)). In contrast to other interstitial cells in the urinary and gastrointestinal tracts, spontaneous Ca(2+) signalling in PICs is uniquely dependent on Ca(2+) influx through I(CaL) channels. A model of prostatic pacemaking is presented describing how I(CaL) can be triggered by an initial membrane depolarization evoked upon the selective opening of Ca(2+)-activated Cl(-) channels by Ca(2+) flowing only through I(CaT) channels. The resulting current flow through I(CaL) results in release of Ca(2+) from internal stores and the summation of Cl(-)-selective spontaneous transient depolarizations (STDs) to form pacemaker potentials that propagate passively into the prostatic stroma to evoke regenerative action potentials and excitation-contraction coupling.