Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents |
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Authors: | Joël Tabak Natalia Toporikova Marc E Freeman Richard Bertram |
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Institution: | (1) Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA;(2) Department of Mathematics, Florida State University, Tallahassee, FL 32306, USA |
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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 ∼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 I
BK and I
A could transform the electrical pattern of activity from spiking to bursting, but through distinct mechanisms. I
BK always increased the intracellular Ca2+ concentration, while I
A 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 a heterogeneous distribution
of fast K+ conductances could cause heterogeneous lactotroph firing patterns.
Action Editor: Christiane Linster |
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Keywords: | Lactotrophs Bursting Calcium Fast/slow analysis |
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