Selective modulation of voltage-gated calcium channels in the terminal nerve gonadotropin-releasing hormone neurons of a teleost, the dwarf gourami (Colisa lalia).
GnRH neurons in the terminal nerve (TN) have been suggested to function as a neuromodulatory system that regulates long-lasting changes in the animal behavior. Here we examined electrophysiological properties of TN-GnRH neurons in a teleost (dwarf gourami, Colisa lalia), focusing on the voltage-gated Ca2+ channels, which are thought to be coupled to several cellular events such as GnRH release. TN-GnRH neurons showed low-voltage activated (LVA) currents and three types of pharmacologically distinct high-voltage activated (HVA) currents. The L- and N-type currents constituted 30.7 +/- 3.1 and 41.0 +/- 3.9%, respectively, of HVA currents, which was recorded at the holding potential of -60 mV to inactivate the LVA currents. Although P/Q-type current was small and negligible, R-type current accounted for the remaining 23.6 +/- 1.6% of HVA currents. Next we examined the possibility of Ca2+ channel modulation induced by GnRH released in a paracrine/autocrine manner. HVA currents of up to 40% was inhibited by the application of salmon GnRH, which is the same molecular species of GnRH as is synthesized by TN-GnRH neurons themselves. However, salmon GnRH had no measurable effects on LVA currents. The inhibition of HVA currents had a dose dependence (EC50 was 11.5 nm) and type specificity among different HVA currents; N- and R-type currents were preferentially inhibited, but L-type currents had by far lower sensitivity. The physiological significance of different Ca2+ influx pathways, and their paracrine/autocrine regulation mechanisms in TN-GnRH neurons are discussed.
Haneda
Kosuke
K
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Oka
Yoshitaka
Y
D000818:Animals; D001921:Brain / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D005399:Fishes / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000378:metabolism*; D012474:Salmon; D013268:Stimulation, Chemical
D015220:Calcium Channels; D007987:Gonadotropin-Releasing Hormone