title: Understanding calcium homeostasis in postnatal gonadotropin-releasing hormone neurons using cell-specific Pericam transgenics.
abstract: The gonadotropin-releasing hormone (GnRH) neurons are the key output cells of a complex neuronal network controlling fertility in mammals. To examine calcium homeostasis in postnatal GnRH neurons, we generated a transgenic mouse line in which the genetically encodable calcium indicator ratiometric Pericam (rPericam) was targeted to the GnRH neurons. This mouse model enabled real-time imaging of calcium concentrations in GnRH neurons in the acute brain slice preparation. Investigations in GnRH-rPericam mice revealed that GnRH neurons exhibited spontaneous, long-duration (~8s) calcium transients. Dual electrical-calcium recordings revealed that the calcium transients were correlated perfectly with burst firing in GnRH neurons and that calcium transients in GnRH neurons regulated two calcium-activated potassium channels that, in turn, determined burst firing dynamics in these cells. Curiously, the occurrence of calcium transients in GnRH neurons across puberty or through the estrous cycle did not correlate well with the assumption that GnRH neuron burst firing was contributory to changing patterns of pulsatile GnRH release at these times. The GnRH-rPericam mouse was also valuable in determining differential mechanisms of GABA and glutamate control of calcium levels in GnRH neurons as well as effects of G-protein-coupled receptors for GnRH and kisspeptin. The simultaneous measurement of calcium levels in multiple GnRH neurons was hampered by variable rPericam fluorescence in different GnRH neurons. Nevertheless, in the multiple recordings that were achieved no evidence was found for synchronous calcium transients. Together, these observations show the great utility of transgenic targeting strategies for investigating the roles of calcium with specified neuronal cell types.
authors.affiliation: Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin 9054, New Zealand.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Constantin
authors.forename: Christine
authors.initials: C
authors.lastname: Jasoni
authors.forename: Nicola
authors.initials: N
authors.lastname: Romanò
authors.forename: Kiho
authors.initials: K
authors.lastname: Lee
authors.forename: Allan E
authors.initials: AE
authors.lastname: Herbison
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D005298:Fertility / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D009474:Neurons / Q000502:physiology*; D009928:Organ Specificity; D011993:Recombinant Fusion Proteins / Q000235:genetics
chemical_list: D020746:Calcium Channels, L-Type; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone