The effects of dopamine receptor agonists on BK_Ca channels and signal transduction mechanism in corpus cavernosal smooth muscle cells

In this study, we investigated the effect of dopamine receptor agonists on potassium channels' activity and their signal transduction pathway in corporal smooth muscle cells. We used cultured human corporal smooth muscle cells. The whole cell and cell-attached configuration of the patch-clamp technique were used for electrophysiological recordings, and enzyme immunoassay was used for measuring cyclic AMP (cAMP) and cyclic GMP levels. Extracellular application of 10 μM dopamine and apomorphine significantly increased whole-cell K ⁺ currents by 283.5±55.7% (at +60 mV; n=12, P<0.001), 292.4±58.8.0% (at +60 mV; n=9, P<0.005), respectively. We confirmed that the increase in whole-cell currents was mainly due to activation of the tetraethylammonium-sensitive large conductance Ca²⁺-activated K ⁺ channels (BK_Ca channels). Enzyme immunoassay indicated that dopamine and apomorphine stimulates cAMP levels in corporal smooth muscle cells in a concentration-dependent fashion. The activation of BK_Ca channels by dopamine receptor agonists in corporal smooth muscle cells might be one of the mechanisms in inducing penile erection.