Haskins J T, Gudelsky G A, Moss R L, Porter J C
Endocrinology. 1981 Mar;108(3):767-71. doi: 10.1210/endo-108-3-767.
The effects of morphine on the release of dopamine from tuberoinfundibular neurons and the release of PRL from the anterior pituitary gland were studied in diestrous female rats. Morphine ions ejected iontophoretically in minute quantities into the arcuate nuclei (using one electrode per nucleus) were found to reduce markedly the concentration of dopamine in hypophysial portal plasma. Thirty minutes after the iontophoretic ejection of morphine using charges of 3.6 and 6.6 millicoulombs/electrode, the concentrations of dopamine in hypophysial portal plasma were reduced 70% and 83%, respectively, relative to the preiontophoretic values. When morphine was iontophoresed into each arcuate nucleus using a charge of 1.5 millicoulombs/electrode, there was no change in the concentration of dopamine in hypophysial portal plasma. The suppressive effect of morphine on dopamine release was prevented by pretreatment of the animals with naloxone (5 mg/kg, ip). In addition to the reduction of the concentration of dopamine in hypophysial portal plasma, the iontophoresis of morphine into the arcuate nuclei enhanced the serum concentration of PRL. On the basis of the present observations, it is suggested that morphine acts on an opiate receptor within the arcuate nucleus to suppress the secretion of dopamine from tuberoinfundibular neurons into hypophysial portal blood, thereby enhancing pituitary gland secretion of PRL.
在动情间期的雌性大鼠中研究了吗啡对结节漏斗神经元多巴胺释放及垂体前叶催乳素释放的影响。发现以微量通过离子电泳法将吗啡离子注入弓状核（每个核使用一个电极）可显著降低垂体门脉血浆中多巴胺的浓度。在使用3.6和6.6毫库仑/电极的电量进行吗啡离子电泳注射30分钟后，垂体门脉血浆中多巴胺的浓度相对于离子电泳前的值分别降低了70%和83%。当以1.5毫库仑/电极的电量将吗啡离子电泳注入每个弓状核时，垂体门脉血浆中多巴胺的浓度没有变化。用纳洛酮（5毫克/千克，腹腔注射）对动物进行预处理可防止吗啡对多巴胺释放的抑制作用。除了降低垂体门脉血浆中多巴胺的浓度外，将吗啡离子电泳注入弓状核还可提高血清催乳素浓度。基于目前的观察结果，提示吗啡作用于弓状核内的阿片受体，抑制结节漏斗神经元向垂体门脉血中分泌多巴胺，从而增强垂体前叶催乳素的分泌。
