DOPAMINE LEVELS IN HYPOPHYSEAL STALK BLOOD IN RAT ARE SUFFICIENT TO INHIBIT PROLACTIN SECRETION INVIVO
DOPAMINE LEVELS IN HYPOPHYSEAL STALK BLOOD IN RAT ARE SUFFICIENT TO INHIBIT PROLACTIN SECRETION INVIVO
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DOI：
10.1210/endo-102-6-1895
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发表时间：
1978-01-01
期刊：
影响因子：
4.8
通讯作者：
NEILL, JD
中科院分区：
文献类型：
--
作者：
GIBBS, DM;NEILL, JD
许多证据表明，多巴胺可以抑制PRL [催乳素]分泌。然而，目前尚不清楚多巴胺是否作用于下丘脑神经元以刺激PRL抑制因子（PIF）的释放，或者多巴胺本身是否是PIF，直接作用于垂体。本研究旨在确定是否通过多巴胺输注抑制PRL分泌，从而产生模拟垂体柄血浆中发现的血浆多巴胺水平。在麻醉的间情期-1大鼠中，茎血浆可帕胺浓度为6.0 ± 0.5mg/kg。1.1 ng/ml（平均值±）SE; n = 10）。在多巴胺输注期间，茎血浆多巴胺水平为动脉水平的70%。以达到9-10 ng/ml动脉水平的速率输注多巴胺，并测量对麻醉雌性大鼠PRL分泌的影响。在间情期大鼠中，多巴胺不抑制PRL分泌。在用α-羟色胺预处理的大鼠中，甲基-p-酪氨酸升高血清PRL水平，多巴胺抑制PRL分泌70%。在PRL水平升高正中隆起病变的大鼠中，多巴胺抑制PRL分泌42%。注入的多巴胺转化为肾上腺素或去甲肾上腺素的量可以忽略不计。在下丘脑多巴胺分泌被阻断的大鼠中，PRL分泌被生理水平的多巴胺抑制（α-甲基-β-酪氨酸处理的）和其中所有下丘脑对垂体的输入被消除的大鼠（正中隆起病变）。这些结果支持多巴胺是直接作用于垂体的生理PIF的假设。
Much evidence indicates that dopamine can inhibit PRL [prolactin] secretion. However, it is still unclear whether dopamine acts on hypothalamic neurons to stimulate PRL-inhibiting factor (PIF) release or whether dopamine is itself PIF, acting directly on the pituitary. This study was designed to determine if PRL secretion is inhibited by dopamine infusions producing plasma dopamine levels which mimic those found in hypophysial stalk plasma. Stalk plasma copamine concentration in urethane-anesthetized diestrus-1 rats was 6.0 .+-. 1.1 ng/ml (mean .+-. SE; n = 10). During a dopamine infusion, stalk plasma dopamine levels were 70% of arterial levels. Dopamine was infused at a rate which achieved arterial levels of 9-10 ng/ml and the effect on PRL secretion in urethane-anesthetized female rats was measured. In diestrus rats, dopamine did not inhibit PRL secretion. In rats pretreated with .alpha.-methyl-p-tyrosine to elevate serum PRL levels, dopamine suppressed PRL secretion 70%. In rats with PRL levels elevated by median eminence lesions, dopamine suppressed PRL secretion 42%. A negligible amount of the infused dopamine was converted to epinephrine or norepinephrine. PRL secretion was inhibited by physiological levels of dopamine in rats in which hypothalamic dopamine secretion was blocked (.alpha.-methyl-p-tyrosine-treated) and in rats in which all hypothalamic input to the pituitary was eliminated (median eminence lesions). These results support the hypothesis that dopamine is a physiological PIF acting directly on the pituitary.