Cationic currents on identified rat gonadotroph cells maintained in primary culture.

Currents and voltage were recorded using the whole-cell patch-clamp technique on gonadotrophs identified by reverse haemolytic plaque assay. In current-clamp experiments, some cells showed spontaneous Ca(2+)-dependent action potentials which were prolonged by inhibition of K(+) currents. In voltage-clamp experiments, a Na(+) current (activated at ?45 mV and up to peak value at +5 mV) and two types of Ca(2+) currents (T- and L-types, respectively activated at ?55 and ?30 mV with a peak current at ?20 and 0 mV) were recorded as inward currents. Three kinds of K(+) currents (outward currents) were recorded; two were voltage-activated, the transient (IKt) and sustained (IKs) and the third was a Ca(2+)-dependent [IK(Ca)]. From these results, we conclude that three ionic currents, i.e. Na(+), Ca(2+) (T- and L-types) and K(+) [IKt, IKs and IK(Ca)], are present in normal rat gonadotrophs.