Placenta on pups' skin accelerates onset of maternal behaviour in non-pregnant rats

Abstract

Previous research has indicated that virgin rats (Rattus norvegicus) behave maternally (sensitize) more rapidly in close proximity with pups. Since both parturient rats and a large percentage of virgin rats avidly consume placenta, we tested whether placenta and amnionic fluid, pups and therefore hasten the onset of maternal behaviour. The results indicated that the procedure indeed shortened the maternal sensitization latency. Furthermore, this effect was not due to the wetness of the pups, to the presence of placenta in the cage, or to the adults having previously ingested placenta. Other attractive ingestibles applied to the pups' skin produced an intermediate, but not significant, shortening of the maternal sensitization latency.

Ingestion of amniotic fluid enhances opiate analgesia in rats

“…Pain threshold has been observed to rise over the course of preg nancy in rats, and this "analgesia of pregnancy" has been demonstrated to be opiate mediated [1,7,8]. Enhancement of such analgesia, therefore, may be one of the principal benefits of parturitional placentophagia, and, in contrast to other hypotheses about advantages (e.g., nest hygiene, mother-infant attachment, reduction of predator-attracting stimuli [14,17]), this hypothesis suggests a benefit that would apply to virtually all species of mammals.However, if placenta, alone, contains the substance that enhances opiate-mediated analgesia during the perinatal period, the fact that placenta is delivered after the neonate (anywhere from 5 to 75 min after) would render it effective only during the delivery of later infants in litters of mothers of polytocous species, or only in the postpartum period in mothers of monotocous species. On the other hand, if the opiate-enhancing substance is also pr~sent in amniotic fluid, then the effect on pain threshold would be realized during, if not before, delivery of the first infant, since amniotic fluid is available to the mother during and often before the emergence of the first infant.…”

“…Pain threshold has been observed to rise over the course of preg nancy in rats, and this "analgesia of pregnancy" has been demonstrated to be opiate mediated [1,7,8]. Enhancement of such analgesia, therefore, may be one of the principal benefits of parturitional placentophagia, and, in contrast to other hypotheses about advantages (e.g., nest hygiene, mother-infant attachment, reduction of predator-attracting stimuli [14,17]), this hypothesis suggests a benefit that would apply to virtually all species of mammals.…”

Maternal and Paternal Perception of Individual Odor Signatures in Human Amniotic Fluid – Potential Role in Early Bonding?

“…Parturient rat dams also exhibit intense interest in AF [9], but it is not as closely associated with parturition as in the ewe. The mere presence of AF on newborn pups accelerates the expression of maternal behavior even in nonpregnant nulliparous female rats which are otherwise avoidant of direct contact with pups [12]. Likewise, AF-wet newborns release higher licking and acceptance rate than dry newborns in parturient ewes and bitches [3,6,8].…”

“…The individually unique quality of AF is further strengthened by the fact that newborn infants themselves are selectively responsive to the odor of AF: when simultaneously exposed to the odors of their own AF and of the AF of an unrelated peer, both breast-and bottle-fed infants orient their head more quickly and for longer duration to the former stimulus than to the latter [21,22]. Comparative data on maternal recognition of the individual quality of the offspring's AF odor are scarce: it has been noticed in one related investigation in sheep [28], but not in rats or in dogs [8,12].…”

“…Their physical, chemical and biological properties have been shown to initiate and sustain infant-directed attention and motivation to lick in the females of a wide array of nonprimate species (e.g., marsupials [2]; ungulates [3][4][5][6][7]; carnivores: [1,8]; rodents [9][10][11][12]). Avid responsiveness to the amniotic fluid (AF) impregnating the fur of their offspring is also a conspicuous feature of the initial behavior of most primate mothers.…”