Buydens P, Velkeniers B, Golstein J, Finné E, Vanhaelst L
Life Sci. 1987 Mar 23;40(12):1207-14. doi: 10.1016/0024-3205(87)90240-2.
It is known that opioids stimulate prolactin (PRL) secretion by an action on hypothalamic neurons, but in vitro studies have suggested a direct action on the lactotrophs. The present study was performed on male rats known to have little or no PRL response to TRH. A beta-endorphin (beta EP) injection in the third ventricle stimulated PRL secretion and induced furthermore a PRL secretory reaction to TRH injected intravenously 20 min later. Pretreatment with naloxone 10 min before beta EP injection abolished not only the PRL response to beta EP but also the conjugated effect of beta EP and TRH. Pretreatment with naloxone methyl bromide (Br-naloxone), a quaternary naloxone derivative, which does not cross the blood-brain barrier, had no effect on the PRL response to beta EP but prevented the conjugated effect of beta EP and TRH on PRL secretion. Pretreatment of the animals with -methyl-parathyrosine resulting in a dopamine depletion or with haloperidol, a dopamine antagonist, could not induce lactotroph responsiveness to TRH. These results suggest that beta EP in male rat sensitizes the PRL cell to TRH by a direct effect and not through an inhibition of the dopaminergic tone.
已知阿片类药物通过作用于下丘脑神经元刺激催乳素（PRL）分泌，但体外研究表明其对催乳细胞有直接作用。本研究在已知对促甲状腺激素释放激素（TRH）几乎没有或没有PRL反应的雄性大鼠上进行。在第三脑室注射β-内啡肽（β-EP）刺激了PRL分泌，并在20分钟后进一步诱导了对静脉注射TRH的PRL分泌反应。在β-EP注射前10分钟用纳洛酮预处理不仅消除了对β-EP的PRL反应，还消除了β-EP和TRH的联合作用。用不能穿过血脑屏障的季铵化纳洛酮衍生物溴化纳洛酮（Br-纳洛酮）预处理，对PRL对β-EP的反应没有影响，但阻止了β-EP和TRH对PRL分泌的联合作用。用导致多巴胺耗竭的α-甲基-对-酪氨酸或多巴胺拮抗剂氟哌啶醇预处理动物，不能诱导催乳细胞对TRH的反应性。这些结果表明，雄性大鼠中的β-EP通过直接作用而非通过抑制多巴胺能张力使PRL细胞对TRH敏感。
