title: Synchronized exocytotic bursts from gonadotropin-releasing hormone-expressing cells: dual control by intrinsic cellular pulsatility and gap junctional communication.
abstract: Periodic secretion of GnRH from the hypothalamus is the driving force for the release of gonadotropic hormones from the pituitary, but the roles of individual neurons in the context of this pulse generator are not known. In this study we used FM1-43 to monitor the membrane turnover associated with exocytosis in single GT1-7 neurons and found an intrinsic secretory pulsatility (frequency, 1.4 +/- 0.1/h; pulse duration, 17.3 +/- 0.6 min) that, during time in culture, became progressively synchronized among neighboring cells. Voltage-gated calcium channels and gap junctional communication each played a major role in synchronized pulsatility. An L-type calcium channel inhibitor, nimodipine, abolished synchronized pulsatility. In addition, functional gap junction communication among adjacent cells was detected, but only under conditions where pulsatile synchronization was also observed, and the gap junction inhibitor octanol abolished both without affecting pulse frequency or duration. Our results, therefore, provide strong evidence that the GnRH pulse generator in GT1-7 cells arises from a single cell oscillator mechanism that is synchronized through network signaling involving voltage-gated calcium channels and gap junctions.
authors.affiliation: Laboratory of Molecular Dynamics, Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: R
authors.initials: R
authors.lastname: Vazquez-Martinez
authors.forename: S L
authors.initials: SL
authors.lastname: Shorte
authors.forename: F R
authors.initials: FR
authors.lastname: Boockfor
authors.forename: L S
authors.initials: LS
authors.lastname: Frawley
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology; D002450:Cell Communication; D002453:Cell Cycle; D002460:Cell Line; D005089:Exocytosis; D017629:Gap Junctions / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D051379:Mice; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
chemical_list: D020746:Calcium Channels, L-Type; C073804:FM1 43; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D007987:Gonadotropin-Releasing Hormone; D002118:Calcium