DOPAMINE LEVELS IN HYPOPHYSEAL STALK PLASMA AND PROLACTIN LEVELS IN PERIPHERAL PLASMA OF THE LACTATING RAT - EFFECTS OF A SIMULATED SUCKLING STIMULUS
DOPAMINE LEVELS IN HYPOPHYSEAL STALK PLASMA AND PROLACTIN LEVELS IN PERIPHERAL PLASMA OF THE LACTATING RAT - EFFECTS OF A SIMULATED SUCKLING STIMULUS
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DOI：
10.1159/000123164
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发表时间：
1981-01-01
影响因子：
4.1
通讯作者：
NEILL, JD
中科院分区：
文献类型：
--
作者：
DEGREEF, WJ;PLOTSKY, PM;NEILL, JD
催乳素的分泌受到下丘脑向垂体门脉系统释放多巴胺的紧张性抑制。然而，生理刺激后多巴胺分泌的变化在改变催乳素分泌中的作用仍然未知。本研究旨在探讨在吸吮诱导的催乳素释放过程中，茎血中多巴胺释放的变化。催乳素分泌的增加，诱导在麻醉，哺乳期大鼠通过15分钟的电刺激一个孤立的乳房神经干。该程序诱导催乳素分泌迅速增加，刺激开始后20-30分钟内观察到催乳素浓度增加7倍。在未受刺激的对照大鼠中，催乳素水平在观察期间保持在基线值。然后，我们测量了这种刺激对垂体柄血浆中多巴胺浓度的影响。在垂体柄血浆中的多巴胺浓度，收集在15分钟的时间间隔之前，期间和之后的乳房神经刺激，刺激过程中显着下降20%，恢复到刺激前的值，然后显着增加20%，在45-60分钟。在对照组大鼠中，多巴胺浓度没有变化。这些结果表明，一个简单的，多巴胺分泌和催乳素分泌之间的反比关系并不存在在哺乳期间。然而，在乳房神经刺激过程中观察到的多巴胺分泌减少可能是一个复杂机制的组成部分，包括其他下丘脑激素，导致催乳素的释放。
Secretion of prolactin is tonically inhibited by hypothalamic release of dopamine into the hypophysial portal system. However, the role that changes in dopamine secretion play in altering prolactin secretion after physiologic stimuli is still unknown. The present study was designed to investigate changes in dopamine release into stalk blood during suckling-induced release of prolactin. An increase in prolactin secretion was induced in urethane-anesthetized, lactating rats by a 15-min electrical stimulation of an isolated mammary nerve trunk. This procedure induced a rapid increase in prolactin secretion, and a 7-fold increase in prolactin concentrations was observed within 20–30 min after stimulation began. In unstimulated control rats, prolactin levels remained at baseline values during the period of observation. Then, we measured the effect of this stimulus on the concentration of dopamine in hypophysial stalk plasma. Dopamine concentrations in hypophysial stalk plasma, collected at 15-min intervals before, during and after mammary nerve stimulation, decreased significantly by 20% during stimulation, returned to prestimulation values, and then increased significantly by 20% at 45–60 min. In control rats, no changes in dopamine concentrations were observed. These results demonstrate that a simple, inverse relationship between dopamine secretion and prolactin secretion does not exist during suckling. However, the observed decrease in dopamine secretion during mammary nerve stimulation may be an integral part of a complex mechanism, including other hypothalamic hormones, that lead to the release of prolactin.