Prostate neuroendocrine (NE) cells play important roles in the growth and differentiation of the prostate. Following enzymatic digestion of rat ventral prostate, the whole-cell patch-clamp technique was applied to dark, round cells that exhibited chromogranin-A immunoreactivity, a representative marker of NE cells. Under zero current-clamp conditions, putative NE cells showed hyperpolarized resting membrane potentials of some 70mV, and spontaneous action potentials were induced by an increase in external [K+] or by the injection of current. Using a CsCl pipette solution, step-like depolarization activated high-voltage-activated Ca2+ current (HVA ICa) and tetrodotoxin-resistant voltage-activated Na+ current. The HVA ICa was blocked by nifedipine and -conotoxin GVIA, L-type and N-type Ca2+ channel blockers, respectively. Using a KCl pipette solution, the transient outward K+ current (Ito), Ca2+-activated K+ currents (IK,Ca), the non-inactivating outward current and an inwardly rectifying K+ current (IKir) were identified. IK,Ca was suppressed by charybdotoxin (50nM), iberiotoxin (10nM) or clotrimazol (1M), but not by apamine (100nM). Ito was inhibited by 4-aminopyridine (5mM). IKir was identified as a Ba2+-sensitive inwardly rectifying current in the presence of a high-K+ bath solution. The voltage- and Ca2+-activated ion channels could play significant roles in the regulation of neurohormonal secretion in the prostate.