Low threshold T-type calcium current in rat embryonic chromaffin cells

Abstract

1. The gating kinetics and functions of low threshold T-type current in cultured chromaffin cells from rats of 19-20 days gestation (E19-E20) were studied using the patch clamp technique. Exocytosis induced by calcium currents was monitored by the measurement of membrane capacitance and amperometry with a carbon fibre sensor. 2. In cells cultured for 1-4 days, the embryonic chromaffin cells were immunohistochemically identified by using polyclonal antibodies against dopamine β-hydroxylase (DBH) and syntaxin. The immuno-positive cells could be separated into three types, based on the recorded calcium current properties. Type I cells showed exclusively large low threshold T-type current, Type II cells showed only high voltage activated (HVA) calcium channel current and Type III cells showed both T-type and HVA currents. These cells represented 44%, 46% and 10% of the total, respectively. 3. T-type current recorded in Type I cells became detectable at -50 mV, reached its maximum amplitude