title: Minimal model for intracellular calcium oscillations and electrical bursting in melanotrope cells of Xenopus laevis.
abstract: A minimal model is presented to explain changes in frequency, shape, and amplitude of Ca2+ oscillations in the neuroendocrine melanotrope cell of Xenopus Laevis. It describes the cell as a plasma membrane oscillator with influx of extracellular Ca2+ via voltage-gated Ca2+ channels in the plasma membrane. The Ca2+ oscillations in the Xenopus melanotrope show specific features that cannot be explained by previous models for electrically bursting cells using one set of parameters. The model assumes a KCa-channel with slow Ca2+-dependent gating kinetics that initiates and terminates the bursts. The slow kinetics of this channel cause an activation of the Kca-channel with a phase shift relative to the intracellular Ca2+ concentration. The phase shift, together with the presence of a Na+ channel that has a lower threshold than the Ca2+ channel, generate the characteristic features of the Ca2+ oscillations in the Xenopus melanotrope cell.
authors.affiliation: Department of Cellular Animal Physiology, Nijmegen Institute for Neurosciences, University of Nijmegen, The Netherlands.
authors.forename: L N
authors.initials: LN
authors.lastname: Cornelisse
authors.forename: W J
authors.initials: WJ
authors.lastname: Scheenen
authors.forename: W J
authors.initials: WJ
authors.lastname: Koopman
authors.forename: E W
authors.initials: EW
authors.lastname: Roubos
authors.forename: S C
authors.initials: SC
authors.lastname: Gielen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology; D007425:Intracellular Membranes / Q000378:metabolism*; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D008959:Models, Neurological; D009991:Oscillometry; D009994:Osmolar Concentration; D010902:Pituitary Gland / Q000166:cytology / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D015222:Sodium Channels; D009074:Melanocyte-Stimulating Hormones; D002118:Calcium