Physiology <S Behavior. Veil. I 8, pp. 495-502. Pergamon Press and Brain Research Puhl.. 1977. Printed in the U.S.A.
Placentophagia in Rats is Modifiable by
Taste Aversion Conditioning'
DOUGLAS B. ENGWall2 AND MARK B. KRISTAL3
Department of Psychology, State University of New York at Buffalo, Buffalo, NY 14226
(Received 6 Augusl 1476)
ENGWALL. I). B. AND M. B. KRISTAL. Placentophagia in rats is modifiable by taste aversion conditioning. PHYSIO!
BEHAV. 18(3) 495 502, 1977. An aversion to placenta Wasconditioned by pairing ingestion with LKTinduced illness,
in virgins, in nonpregnant primipara, and in primipara during the first parturition. Persistence of the aversion was assessed
at the subsequent parturition, immediately after the subsequent parturition, and two weeks after the subsequent
parturition. The results indicated that (a) female rats can learn an aversion to placenta, <b) the aversion was expressed
during parturition, (c) previous parturitional experience reduced retention of the aversion, but not acquisition, (d) ratscan
distinguish between their own normally delivered placenta and donor placenta, and (e) an aversion to placenta at
parturition did not appear to have a major effect on pup care.
Placentophagia Tasteaversionconditioning Maternalbehavior Rals Iithiumchloride
PREVIOUS Sludies have demonstrated the difficulty in
distinguishing Ihe maternal behavior of Ihe experienced,
multiparous female rat from her inexperienced, primiparous
counterpart ∣8]. The importance of prior parturitional
experience can. however, be observed under atypical
breeding conditions brought about by ovariectomy ∣9∣ and
olfactory bulbectomy ∣l∣. The experience of raising the
first litter buffers the parturient female against the disrup-
tive effects of the atypical physiological conditions.
The present experiments were undertaken, in part, to
investigate the effects of experience on the specific mater-
nal behavior of placentophagia, the consumption of the
afterbirth by the parturient female. Placentophagia usually
occurs only under the peculiar hormonal and behavioral
conditions of parturition, and can be considered both as an
ingestive and a maternal behavior.
In a study of the relationship between placentophagia
and homeostatic feeding, Kristal ∣4∣ produced lesions of
the lateral hypothalamus (LH) in pregnant and nonpregnant
rats. Despite the aphagia demonstrated by all the animals
with lesions, mulliparae continued to eat placenta at
parturition, whereas primiparae did not. Kristal also found
that virgins did not ingest donor placenta after receiving
lesions, whereas nonpregnant ιnultiparae continued to eat
placenta after becoming otherwise aphagic. Kristal con-
cluded that prior parturitional experience with placenta,
and not pregnancy per se. was the critical factor influencing
the occurrence of placentophagia after LH lesions.
A certain proportion of nonpregnant rats and mice will
eat placenta that has been obtained from donor females [4,
5. 6, 7.∣. Recent studies have shown increases in placento-
phagia as a function of parity in Long-Evans rats [6∣. Ihe
proportion of females exhibiting placentophagia in the
nonpregnant state as related to parity was as follows:
nulliparous, 0.47; primiparous. 0.62; multiparous. 0.76.
Thus the influences of parity on placentophagia can be seen
in both the parturient and the nonpregnant conditions.
In discussing the motivational factors that might inhibit
placentophagia in virgin female mice, Kristal and Elef-
Iheriou I 5∣ suggested that neophobia or aversion might be
competing with the initiation of placentophagia. The
competing avoidance response appeared to be overriden by
the behavioral and/or hormonal events which surround
parturition, since nearly every female rodent consumes
placenta during her first normal parturition. The subse-
quent ingestive response to placenta was altered as a result
Ofparturilional experience with placenta.
Since taste aversion conditioning (hereafter, for the sake
of brevity, TAC) has been used to investigate the develop-
ment of ingestive preferences ∣2], the application of TAC
techniques seemed a logical approach to the study of
placentophagia. TAC involves the pairing of a novel taste
with gastrointestinal distress brought about by the adminis-
tration of a toxic agent. Eor the present experiments, the
consumption of placenta was paired with the administra-
tion of lithium chloride (LiCI). a very effective malaise-
inducing agent I I OI.
Novelty has been found to be of great importance in
assuring the effectiveness of TAC. Rats learn aversions to
novel substances much more readily than to familiar ones
'Supported in part by National Institute of Mental Health Small Grant Mil-25747, in part by National Science Ioundation Grant
BNS76∙O43I6. and in part by Institutional I unds from SUNY al Buffalo, all awarded to M. B. K. We wish to thank Seymour Axelrod for
his helpful comments on an earlier version of the manuscript.
2Present address: Department of Psychology. Central Connecticut Stale College. New Britain. CT ()6()50.
’Send reprint requests Io: Mark B. Kristal. Department of Psychology, SUNY at Buffalo. 4230 Ridge Lea. Buffalo. NY I422(>.
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