Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents
Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents
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DOI：
10.1007/s10827-006-0008-4
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发表时间：
2007-04-01
影响因子：
1.2
通讯作者：
Bertram, Richard
中科院分区：
文献类型：
--
作者：
Tabak, Joel;Toporikova, Natalia;Bertram, Richard
下丘脑释放的多巴胺（DA）强直性抑制垂体乳营养物。DA（在微摩尔浓度下）打开钾通道，使乳养菌超极化，从而防止触发催乳素激素释放的钙流入。令人惊讶的是，在浓度低于1000的情况下，DA可以刺激催乳素分泌。在这里，我们研究了K+电流的增加是否可以介导这种刺激作用。我们考虑了通过大电导BK通道和通过a型通道的快速K+电流。我们开发了一个最小的乳营养模型来研究这两种电流的影响。I （BK）和I (A)都可以将电活动模式从尖峰转变为爆发，但通过不同的机制。I （BK）能使细胞内Ca2+浓度升高，而I- a能使细胞内Ca2+浓度升高或降低。因此，DA的刺激作用可能是由快速的K+传导介导的，它将强直尖峰细胞转化为爆裂细胞。此外，该研究表明，快速K+电导的不均匀分布可能导致不均匀的滋养乳细胞放电模式。
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 similar to 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.