Effects of extracellular Ca2+ influx and intracellular Ca2+ release on ethanol-induced cytoplasmic Ca2+ overload in cultured superior cervical ganglion neurons

The present research was designed to investigate the interference of Ca2+ homeostasis by ethanol on the primary cultured superior cervical ganglion (SCG) neurons. (1) Using the whole cell patch clamp recording, the amplitudes of voltage-dependent Ca2+ channel (VDCC) currents could be reduced by ethanol in a concentration-dependent manner. Ethanol (100 mM) inhibited about 25% of Ca2+ channel current. However, the activation of Ca2+ channel was not affected by ethanol at those concentrations. (2) The similar extent inhibitions of 100 mM ethanol on the increments of intracellular Ca2+ concentration ([Ca2+]i) induced by 40 mM KCl and 1 μM A23187 were also observed in the fluo-3-AM loaded superior cervical ganglia (SCG) via detecting the change of [Ca2+]i with a laser scanning confocal microscopy. In contrast, the basal [Ca2+]i was significantly increased by ethanol alone in a concentration-dependent manner. These phenomena were also observed even under Ca2+ free bath solution or the solution added 300 μM cadmium chloride conditions. Together with above results, our data suggest that ethanol increases basal [Ca2+]i, but it also inhibits the extracellular Ca2+ influx through VDCC and ionophore channel. And the augment of basal [Ca2+]i induced by ethanol might attribute to the Ca2+ releasing from intracellular Ca2+ pools.