Inhibition of release of neurohypophysial hormones by endogenous opioid peptides in pregnant and parturient rats.
Inhibition of release of neurohypophysial hormones by endogenous opioid peptides in pregnant and parturient rats.
复制标题
内源性阿片肽对妊娠和产妇大鼠神经垂体激素释放的抑制作用。
DOI：
10.1016/0006-8993(86)91344-2
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发表时间：
1986
期刊：
影响因子：
2.9
通讯作者：
Summy-Long,JY
中科院分区：
文献类型：
--
作者：
Hartman,RD;Rosella-Dampman,LM;Emmert,SE;Summy-Long,JY
用阿片受体拮抗剂纳洛酮研究了阿片肽对大鼠胚胎排出后催产素（OT）和加压素（AVP）释放的影响。本实验测定了纳洛酮（5 mg/kg，s.c.）或生理盐水，在妊娠第20天和第21天，在分娩的排出阶段之前或期间。间情期未孕大鼠给予纳洛酮作对照。在妊娠第20天和第21天，分娩开始前，与未妊娠对照组相比，血浆[AVP]升高，但[OT]未升高。在前两只幼仔分娩后，血浆[OT]约加倍，而血浆[AVP]保持不变。用纳洛酮阻断内源性阿片肽的作用，导致妊娠动物在妊娠第20天和第21天以及分娩期间血浆[OT]升高。纳洛酮，但是，没有改变血浆[AVP]在临产或临产动物。与此相反，[AVP]，而不是[OT]，在非妊娠大鼠血浆中增加纳洛酮。妊娠和非妊娠大鼠神经中间叶中OT的含量相似，并且不影响前两只幼仔的分娩。而妊娠动物分娩前垂体AVP含量及AVP/OT比值均低于未妊娠对照组。纳洛酮对上述两种激素的含量均无影响。因此，AVP释放明显增加，垂体储存的这种肽在妊娠第20天减少，此时分娩尚未开始。相反，OT分泌仅在分娩期间升高。阿片肽抑制OT释放可能：（1）允许妊娠期间优先释放AVP;（2）防止大鼠分娩1-2 h期间垂体OT储存耗尽和神经元疲劳。
Naloxone, an opiate receptor antagonist, was used to determine whether opioid peptides modulate release of oxytocin (OT) or vasopressin (AVP) in the rat after expulsion of the fetus, i.e. parturition. We measured the concentrations of AVP and OT in plasma and in the neurointermediate lobe of the pituitary of pregnant rats given naloxone (5 mg/kg, s.c.) or saline on day 20 of gestation, and on day 21 either before or during the expulsive stage of labor. Non-pregnant rats in diestrus were giben naloxone for comparison. On days 20 and 21 of gestation, before the onset of parturition, plasma [AVP] but not [OT] was elevated, compared to the non-pregnant controls. After delivery of the first two pups, plasma [OT] approximatelyy doubled, whereas plasma [AVP] remained unchanged. Blocking the action of endogenous opioid peptides with naloxone caused an elevation of plasma [OT] in pregnant animals on days 20 and 21 of gestation and during parturition. Naloxone, however, did not alter plasma [AVP] in either parturient or preparturient animals. In contrast, [AVP], but not [OT], was increased in plasma of non-pregnant rats given naloxone. The content of OT in the neuro-intermediate lobe was similar in pregnant and non-pregnant rats and was unaffected delivery of the first two pups. However, AVP content and the ratio of AVP/OT in the pituitary were lower in pregnant animals before during delivery than in the non-pregnant controls. The content of neither hormone was altered by naloxone. Thus, AVP release apparently increase and pituitary stores of this peptide are decreased by day 20 gestation, when labor has not yet begun. In contrast, OT secretion becomes elevated only during delivery. Inhibition of OT release by opioid peptides may: (1) allow preferential release of AVP during pregnancy; and (2) prevent depletion of pituitary stores of OT and neuronal fatigue during the 1–2 h period of parturition in the rat.