Kristal M B, Thompson A C, Abbott P
Physiol Behav. 1986;38(6):809-15. doi: 10.1016/0031-9384(86)90047-8.
Placenta ingestion has recently been shown to enhance opiate-mediated analgesia produced by morphine injection, footshock, or vaginal/cervical stimulation. The enhancement of the effect of endogenous opiates (especially analgesia) may be one of the principal benefits to mammalian mothers of placentophagia at delivery. During labor and delivery, however, mothers also ingest amniotic fluid (AF) which, unlike placenta, becomes available during, or even before expulsion of the infant. The present experiments were undertaken to determine whether AF ingestion, too, enhances analgesia; if so, whether the effect requires ingestion of, or merely exposure to, AF; whether the effect can be produced by AF delivered directly to the stomach by tube; and whether the enhancement, if it exists, can be blocked by administering an opiate antagonist. Nulliparous Long-Evans rats were tested for analgesia using tail-flick latency. We found that rats that ingested AF after receiving a morphine injection showed significantly more analgesia than did rats that ingested a control substance; AF ingestion, alone, did not produce analgesia; ingestion of AF, rather than just smelling and seeing it, was necessary to produce analgesia enhancement; AF produced enhancement when oropharyngeal factors were eliminated by delivering it through an orogastric tube; and treatment of the rats with naltrexone blocked the enhancement of morphine-induced analgesia that results from AF ingestion.
最近的研究表明，吞食胎盘可增强吗啡注射、电击足部或阴道/宫颈刺激所产生的阿片类药物介导的镇痛作用。内源性阿片类药物作用（尤其是镇痛作用）的增强可能是哺乳动物母亲在分娩时吞食胎盘的主要益处之一。然而，在分娩过程中，母亲们也会摄入羊水，与胎盘不同的是，羊水在婴儿排出期间甚至之前就已可得。本实验旨在确定摄入羊水是否也能增强镇痛作用；如果是，这种作用是需要摄入羊水，还是仅仅接触羊水即可；通过管子直接将羊水输送到胃中是否能产生这种作用；以及如果存在这种增强作用，是否可以通过给予阿片拮抗剂来阻断。使用无经验的长 Evans 大鼠通过甩尾潜伏期来测试镇痛效果。我们发现，在注射吗啡后摄入羊水的大鼠比摄入对照物质的大鼠表现出明显更强的镇痛作用；单独摄入羊水不会产生镇痛作用；必须摄入羊水，而不仅仅是闻到和看到羊水，才能增强镇痛作用；当通过口胃管输送羊水消除口咽因素时，羊水会产生增强作用；用纳曲酮治疗大鼠可阻断因摄入羊水而导致的吗啡诱导镇痛作用的增强。
