Voltage-dependent ion channel currents in putative neuroendocrine cells dissociated from the ventral prostate of rat

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 -70 mV, 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 I(Ca)) and tetrodotoxin-resistant voltage-activated Na+ current. The HVA I(Ca) was blocked by nifedipine and omega-conotoxin GVIA, L-type and N-type Ca2+ channel blockers, respectively. Using a KCl pipette solution, the transient outward K+ current (I(to)), Ca2+ -activated K+ currents (I(K,Ca)), the non-inactivating outward current and an inwardly rectifying K+ current (I(Kir)) were identified. I(K,Ca) was suppressed by charybdotoxin (50 nM), iberiotoxin (10 nM) or clotrimazol (1 microM), but not by apamine (100 nM). I(to) was inhibited by 4-aminopyridine (5 mM). I(Kir) 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.