Placenta ingestion enhances opiate analgesia in rats.

Abstract

Analgesia, produced by either a morphine injection or footshock, was monitored (using a tail-flick test) in nonpregnant female rats. Analgesia was induced within minutes of having the rats eat on of several substances. When the substance eaten was rat placenta, both the morphine- and shock-induced types of analgesia were significantly grater than in controls that ingested other substances (or nothing). When footshock (hind-paw) was administered in conjunction with the opiate antagonist naltrexone, the analgesia produced was attenuated but detectable; in this case, placenta ingestion did not enhance the analgesia, suggesting that the effect of placenta is specific to opiate-mediated analgesia. It is possible that this enhancement of analgesia is one of the principal benefits to mammalian mothers of ingesting placenta and birth fluids (placentophagia) at delivery.