Effects of Noradrenaline on the Membrane Potential of Prostatic Neuroendocrine Cells of Rat

Kim, Jun Hee; Shin, Sun Young; Uhm, Dae Yong; Kim, Sung Joon

Abstract

The prostate gland contains numerous neuroendocrine cells that are believed to influence the function of the prostate gland. Our recent study demonstrated the expression of both alpha 1- and alpha 2-ARs, signaling the release of stored Ca2+ and the inhibition of N-type Ca2+ channels, respectively, in rat prostate neuroendocrine cells (RPNECs). In this study, the effects of NA on the resting membrane potential (RMP) of RPNECs were investigated using a whole-cell patch clamp method. Fresh RPNECs were dissociated from the ventral lobe of rat prostate and identified from its characteristic shape; round or oval shape with dark cytoplasm. Under zero-current clamp conditions with KCl pipette solution, the resting membrane potential (RMP) of RPNECs was between 35 mV and 85 mV. In those RPNECs with relatively hyperpolarized RMP (< 60 mV), the application of noradrenaline (NA, 1 micro M) depolarized the membrane to around 40 mV. In contrast, the RPNECs with relatively depolarized RMP (> 45 mV) showed a transient hyperpolarization and subsequent fluctuation at around 40 mV on application of NA. Under voltage clamp conditions (holding voltage, 40 mV) with CsCl pipette solution, NA evoked a slight inward current (< 20 pA). NA induced a sharp increase of cytosolic Ca2+ concentration ([Ca2+]c), measured by the fura-2 fluorescence, and the voltage clamp study showed the presence of charybdotoxin-sensitive Ca2+ -activated K+ currents. In summary, adrenergic stimulation induced either depolarization or hyperpolarization of RPNECs, depending on the initial level of RMP. The inward current evoked by NA and the Ca2+ -activated K+ current might partly explain the depolarization and hyperpolarization, respectively.