title: Kisspeptin inhibits high-voltage activated Ca2+ channels in GnRH neurons via multiple Ca2+ influx and release pathways.
abstract: Kisspeptin plays an important role in puberty and subsequent fertility by activating its receptor, G-protein-coupled receptor 54 (GPR54), and increasing cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) and gonadotropin-releasing hormone (GnRH) secretion in GnRH neurons. Yet the mechanism by which kisspeptin increases [Ca(2+)](i) in GnRH neurons remains to be fully elucidated. In other neurons, voltage-gated Ca(2+) channel (VGCC) activity has been shown to be inversely related to [Ca(2+)](i). We used whole-cell patch-clamp recording to examine the effects of kisspeptin-10 (KP-10) on VGCC activity evoked by step depolarizations in GnRH neurons in brain slices from pubertal male GnRH-green fluorescent protein transgenic mice. Prolonged (>30 s) KP-10 application inhibited Ca(2+) currents. The GPR54 antagonist peptide 234, chelation of intracellular Ca(2+) by 1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid, substitution of Ba(2+) for Ca(2+), the calmodulin antagonists calmidazolium and trifluoperazine, the phospholipase C inhibitor edelfosine, the canonical transient receptor potential (TRPC) channel and inositol 1,4,5-trisphosphate receptor (IP(3)R) antagonist 2-APB, the TRPC channel antagonist BTP2 and the endoplasmic reticulum Ca(2+)-ATPase blocker cyclopiazonic acid each prevented inhibition. The IP(3)R antagonists caffeine (10 µM), heparin and intracellular 2-APB prevented inhibition to a lesser extent. The ryanodine receptor (RyR) antagonists ryanodine and dantrolene prevented inhibition, and the RyR agonist caffeine (30 mM) mimicked the effects of KP-10 on Ca(2+) currents. Our results suggest that kisspeptin induces Ca(2+) influx through TRPC channels and Ca(2+) release via IP(3)Rs and RyRs, and that this is followed by Ca(2+)/CaM-dependent inhibition of VGCCs.
authors.affiliation: Section of Endocrinology, Department of Medicine, University of Chicago, Chicago, Ill., USA.
authors.forename: Xiao-Bing
authors.initials: XB
authors.lastname: Zhang
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Spergel
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D059648:Kisspeptins / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; C106628:KISS1 protein, human; D059648:Kisspeptins; D007987:Gonadotropin-Releasing Hormone