Inward membrane currents and electrophysiological responses to GnRH in ovine gonadotropes

Abstract

We have used conventional whole-cell patch-clamp to investigate the membrane currents of ovine anterior pituitary gonadotropes, and nystatin-perforated whole-cell patch-clamp to record the membrane potential changes elicited by the natural hypothalamic secretagogue, gonadotropin-releasing hormone (GnRH). A large basal inward current found by voltage clamp was blocked by tetrodotoxin (TTX) (ED50 < 10nM), identifying it as a Na+ current. Slowly inactivating inward current, activated at potentials more positive than –30 mV, remained in Na+-free medium or in the presence of 1 µM TTX. This current was abolished by ionic Ca2+ channel blockade. In the presence of nifedi-pine about 70% of this high ..