Bicknell R J, Leng G, Russell J A, Dyer R G, Mansfield S, Zhao B G
Department of Neuroendocrinology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, U.K.
Brain Res Bull. 1988 Jun;20(6):743-9. doi: 10.1016/0361-9230(88)90086-x.
The influences of opioids on oxytocin secretion and parturition were investigated in the rat. Morphine, administered centrally or peripherally, severely delays the course of established parturition. This delay is accompanied by reduced plasma oxytocin levels and is overcome by treatment either with the opioid antagonist naloxone, or by infusion of oxytocin. An endogenous opioid regulatory mechanism inhibiting oxytocin secretion becomes activated immediately prior to and during parturition. This mechanism does not operate earlier in pregnancy or during normal lactation and is not seen in nonpregnant animals. Naloxone acutely speeds up the course of established parturition, an effect accompanied by greatly elevated plasma oxytocin levels. The mechanisms underlying opioid regulation of oxytocin neurones were investigated at two sites. Precipitated withdrawal from chronic morphine treatment causes hypersecretion of oxytocin. This response is mediated by greatly enhanced electrical activity in the perikarya of oxytocin neurones indicating the presence of opioid receptors on oxytocin neurones and/or on their afferent input. Opioid receptors are also present in the neurohypophysis where they exert direct and noradrenaline mediated effects on secretion from oxytocin terminals in vitro.
在大鼠中研究了阿片类药物对催产素分泌和分娩的影响。中枢或外周给予吗啡会严重延迟已确立的分娩进程。这种延迟伴随着血浆催产素水平降低，并且通过使用阿片类拮抗剂纳洛酮治疗或输注催产素可克服。一种抑制催产素分泌的内源性阿片调节机制在分娩前和分娩期间立即被激活。这种机制在妊娠早期或正常哺乳期间不起作用，在未怀孕的动物中也未观察到。纳洛酮可急性加速已确立的分娩进程，这种效应伴随着血浆催产素水平大幅升高。在两个部位研究了阿片类药物对催产素神经元调节的机制。慢性吗啡治疗后突然戒断会导致催产素分泌过多。这种反应是由催产素神经元胞体中大大增强的电活动介导的，表明催产素神经元和/或其传入输入上存在阿片受体。阿片受体也存在于神经垂体中，在体外它们对催产素终末的分泌发挥直接和去甲肾上腺素介导的作用。
