title: Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents.
abstract: Dopamine (DA) released from the hypothalamus tonically inhibits pituitary lactotrophs. DA (at micromolar concentration) opens potassium channels, hyperpolarizing the lactotrophs and thus preventing the calcium influx that triggers prolactin hormone release. Surprisingly, at concentrations approximately 1000 lower, DA can stimulate prolactin secretion. Here, we investigated whether an increase in a K+ current could mediate this stimulatory effect. We considered the fast K+ currents flowing through large-conductance BK channels and through A-type channels. We developed a minimal lactotroph model to investigate the effects of these two currents. Both IBK and IA could transform the electrical pattern of activity from spiking to bursting, but through distinct mechanisms. IBK always increased the intracellular Ca2+ concentration, while IA could either increase or decrease it. Thus, the stimulatory effects of DA could be mediated by a fast K+ conductance which converts tonically spiking cells to bursters. In addition, the study illustrates that
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA. joel@neuro.fsu.edu
authors.forename: Joël
authors.initials: J
authors.lastname: Tabak
authors.forename: Natalia
authors.initials: N
authors.lastname: Toporikova
authors.forename: Marc E
authors.initials: ME
authors.lastname: Freeman
authors.forename: Richard
authors.initials: R
authors.lastname: Bertram
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D052682:Lactotrophs / Q000187:drug effects*; D008954:Models, Biological; D010902:Pituitary Gland / Q000166:cytology*; D011188:Potassium / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*
chemical_list: D024681:Potassium Channels, Calcium-Activated; D011388:Prolactin; D011188:Potassium; D002118:Calcium; D004298:Dopamine