title: Gonadotropin-releasing hormone induces oscillatory membrane currents in rat gonadotropes.
abstract: Electrophysiological studies were performed to characterize membrane currents of rat gonadotropes under basal conditions and after exposure to secretagogues. Gonadotropes were identified in primary cultures of rat anterior pituitaries by a reverse hemolytic plaque assay. Giga-seal patch clamp recording with the cell-attached configuration was used to monitor membrane currents in these cells. Spontaneous spikes in basal current were seen. These were blocked by methoxyverapamil and probably reflect Ca2+-dependent action potentials. Brief GnRH stimulation induced slow oscillatory changes in membrane current that evolved into a series of large amplitude inward pulses after about 8 min. Treatment with TRH had no effect, and depolarization with K+ led to delayed inward currents without any oscillatory behavior. Under conditions of Ca2+ channel blockade, GnRH stimulation did not induce pulses of inward current, but did lead to oscillatory activation of a small conductance ion channel apparently selective for K+. Taken together these results suggest that GnRH induces oscillations in intracellular Ca2+ and that these oscillations are controlled by biochemical processes.
mesh_terms: D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007774:Lactation; D007986:Luteinizing Hormone / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D011188:Potassium