Nussinovitch I, Kleinhaus A L
Department of Anatomy, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Brain Res. 1992 Mar 6;574(1-2):49-55. doi: 10.1016/0006-8993(92)90798-e.
Several lines of evidence suggest that dopamine acts as a neurotransmitter that inhibits both hormone secretion and electrical activity in pituitary intermediate cells (melanotrophs). In this study we examined the effects of exogenously applied dopamine on voltage activated calcium currents recorded with the whole-cell mode of the patch-clamp technique from short-term primary cultures of melanotrophs. Two types of calcium currents were distinguished by their voltage dependence and kinetics of inactivation similar to the low voltage-activated currents (LVA; or T-type) and high voltage-activated currents (HVA; N&L-types) of calcium currents. Exogenously applied dopamine (2-20 microM) reversibly reduced both LVA and HVA types of calcium currents. Evidence for these results came from experiments in which LVA and HVA calcium currents were separated by stepping to different membrane potentials from a fixed holding potential (Vh) or by changing Vh. These results suggest that dopamine can regulate the entry of calcium into melanotrophs by acting on at least two different populations of calcium channels thereby affecting hormone secretion and electrical activity.
多项证据表明，多巴胺作为一种神经递质，可抑制垂体中间细胞（黑素细胞）的激素分泌和电活动。在本研究中，我们使用膜片钳技术的全细胞模式，从黑素细胞短期原代培养物中记录了外源性应用多巴胺对电压激活钙电流的影响。根据其电压依赖性和失活动力学，区分出两种类型的钙电流，类似于钙电流中的低电压激活电流（LVA；或T型）和高电压激活电流（HVA；N型和L型）。外源性应用多巴胺（2 - 20 microM）可可逆性降低LVA和HVA两种类型的钙电流。这些结果的证据来自于通过从固定钳制电位（Vh）跃迁至不同膜电位或改变Vh来分离LVA和HVA钙电流的实验。这些结果表明，多巴胺可通过作用于至少两种不同的钙通道群体来调节钙进入黑素细胞，从而影响激素分泌和电活动。
