Robinson T M, Abbott P, Kristal M B
Department of Psychology, State University of New York at Buffalo 14260-4110, USA.
Physiol Behav. 1995 Feb;57(2):261-3. doi: 10.1016/0031-9384(94)00238-z.
Ingestion of placenta or amniotic fluid by rats has been shown to enhance ongoing opioid-mediated antinociception, but does not, by itself, produce antinociception. This enhancement is produced by an active substance(s) in placenta and amniotic fluid that we have termed POEF for placental opioid-enhancing factor. Previous research has shown that enhancement requires mediation by the gastrointestinal system: gastric vagotomy blocks enhancement produced by ingested placenta; amniotic fluid injected SC or IP does not produce enhancement. The present study was designed to distinguish between two possible explanations for the blockade of the POEF effect produced by gastric vagotomy: that afferent information arising in vagal gastric receptors conveys the critical information to the CNS, or that disruption of vagal efferent action on digestion blocks the manufacture or activation of the POEF molecule in the gut. Famotidine is an H2-histamine receptor antagonist that reduces gastric acid and pepsin secretion to an extent at least as great as gastric vagotomy. Rats treated with either famotidine or a vehicle were fed placenta or a control substance, then stimulated with vaginal/cervical probing to produce antinociception that is partly opioid mediated. Famotidine did not block POEF enhancement of vaginal/cervical stimulation-induced analgesia in a tail flick latency test. These results suggest that enhancement by POEF does not require normal digestive processes or other processes inhibited by famotidine.
已证实，大鼠摄入胎盘或羊水可增强正在进行的阿片类药物介导的镇痛作用，但胎盘或羊水本身不会产生镇痛作用。这种增强作用是由胎盘和羊水中的一种活性物质产生的，我们将其称为胎盘阿片增强因子（POEF）。先前的研究表明，这种增强作用需要胃肠道系统的介导：胃迷走神经切断术可阻断摄入胎盘所产生的增强作用；皮下或腹腔注射羊水不会产生增强作用。本研究旨在区分胃迷走神经切断术阻断POEF效应的两种可能解释：即迷走神经胃受体产生的传入信息将关键信息传递至中枢神经系统，或者迷走神经对消化的传出作用中断会阻断肠道中POEF分子的产生或激活。法莫替丁是一种H2组胺受体拮抗剂，其减少胃酸和胃蛋白酶分泌的程度至少与胃迷走神经切断术相同。用 either 法莫替丁或赋形剂处理的大鼠喂食胎盘或对照物质，然后通过阴道/宫颈探查进行刺激以产生部分由阿片类药物介导的镇痛作用。在甩尾潜伏期试验中，法莫替丁并未阻断POEF对阴道/宫颈刺激诱导的镇痛作用的增强。这些结果表明，POEF的增强作用不需要正常的消化过程或法莫替丁所抑制的其他过程。
