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FRANZ ET AL.
ing over pups were noted. Afterward, any existing nest was
destroyed, and 1 hr later the presence or absence of a rebuilt
nest was noted.
On each of the next five days, at 0900 hr, each mother was
weighed and her pups removed and replaced with a group of
four freshly nourished pups. Maternal behavior and nest-
building tests were conducted twice daily, between 0900 and
1000 hr and between 2100 and 2200 hr. A total of 11 tests was
conducted; the first test on which nestbuilding or any com-
ponent of maternal behavior was observed was taken to be
the latency for the onset of that behavior. After Test 11 on
postpartum Day 5, each mother was separated from her pups
and placed into a wire-mesh cage with food and water.
Test for hyperphagia. To determine whether hyperphagia
was produced by the knife cuts, measurements of food in-
take, water intake, and body weight were taken daily for 10
days beginning on the third day. after the rats were trans-
ferred to wire-mesh cages. These measurements were ini-
tiated at this time, rather than immediately after surgery, in
order to avoid the confounding effects on food intake of the
increased energy requirements associated with gestation and
lactation [14]. The З-day interval between weaning of pups
and initiation of testing was chosen on the basis of Fleming’s
finding [14] that the elevated level of food intake charac-
teristic of lactating females does not decline to premating
levels until 24-48 hr after weaning.
During the test period, the rats were maintained on tap
water and a high-fat diet, available ad lib, consisting of two
parts ground laboratory chow and one part vegetable
shortening (Crisco). This diet is highly palatable to rats, and
therefore provides a sensitive measure Ofhyperphagia [12].
The food was presented in baby food jars attached to the
front of each cage. Foodjars and water bottles were weighed
daily, and food and water intakes were determined by cal-
culating difference weights over each 24-hr period. Daily food
intake was corrected for spillage. The day on which a rat was
first exposed to the high-fat diet was designated Day 0 of
hyperphagia testing. Intake and body weight measures were
continued through Day 10.
Histological analysis. At the conclusion of the test for
hyperphagia, rats with knife cuts were anesthetized with an
overdose of pentobarbital and perfused intracardially with
physiological saline followed by 10% formalin. The brains
were then removed, fixed in formalin, cut at 40 μ on a cryo-
stat, and every fifth section stained with cresyl violet or
formal-thionin. The location and extent of the knife cuts
were then verified microscopically.
RESULTS
For statistical analyses, data from the ASYM-Control
Group were pooled with data from the MPO and MFB sham
groups, since these groups were not different from one an-
other.
The analysis of the effect of pre-breeding response to
placenta was performed before ASYM subjects were run.
The design was a 2×3 design (Placenta Predisposition
[placentophage∕nonplacentophage] × Knife Cut [MP0,
MFB, SHAM]). When we determined that there were no
significant main or interaction effects of placenta predisposi-
tion on placentophagia or maternal behavior, data from
placentophages and nonplacentophages were pooled for all
subsequent analyses. Because placenta predisposition had
no effect, and because placentophages make up the large
majority of our colony, all the rats receiving ASYM cuts
were placentophages.
Postoperative Food and Water Intake
Nine rats (3/15 with MPO cuts, 5/17 with MFB cuts, and
1/9 with ASYM cuts) were dropped from the experiment on
Day 21 of pregnancy due to extreme debilitation, which in-
cluded aphagia and adipsia. Subsequent histological exam-
ination revealed that debilitation was probably caused by
incorrectly placed knife cuts, many of which produced
hemorrhaging and/or widespread hypothalamic damage. For
each of the remaining rats, 24-hr postoperative food and
water intakes were calculated as percentages of Day-20
body weight for groups of primiparous rats with MPO,
MFB, ASYM, and SHAM cuts. An analysis of variance indi-
cated a significant effect of surgery on food intake,
F(3,49) = 3.67, p<0.01, with food intakes (mean percentage
of body weight) of 4.8±0.7%; 7.7±0.9%; 8.3±1.3%; and
5.9±0.5%, for MPO, MFB, ASYM, and SHAM Groups, re-
spectively. Subsequent pairwise comparisons (all pairwise
comparisons after ANOVAs were done by a Newman-Keuls
test, ps<0.05) revealed that rats with MPO cuts ate signifi-
cantly less than those with MFB or ASYM cuts, but not
significantly less than the SHAM Group. The MFB and
ASYM Groups did not eat significantly more than the SHAM
Group. There were no significant differences in water intake
among the four groups, F(3,49)= 1.16, p>0.05. Mean water
intake (percentage of body weight) ranged from 13.0±1.0%
for the SHAM Group to 17.7±2,7% for the ASYM Group.
Tinting of Parturition and Condition of Offspring
There were no statistically significant differences among
the four surgical groups with respect to the duration of par-
turition, F(3,49) = 1.45, p>0.05. Mean durations ranged from
74.6±8.2 min for the MPO Group to 107.9±23.3 min for the
ASYM Group. The data on gestation length were computed
as percentages of each group that delivered in each hour on
Day 22, Day 23, or Day 24 of pregnancy. ANOVA revealed
that there were no statistically significant differences among
the four surgical groups, F(3,49)<1.0. Based on data
gathered across all 4 groups, 15.1% of the rats delivered on
Day 22, 64.15% delivered on Day 23 and 20.75% delivered on
Day 24.
There were no significant differences among the four
surgical groups with respect to litter size, F(3,49)<1.0
(means ranged from 8.9±1.1 pups for the,ASYM Group to
9.9±1.0 for the SHAM Group); percentage of each litter
born alive, F(3,49)=2.2, p>0.05 (means ranged from
54.9± 11.3% for the MPO Group to 84.3 ±4.8% for the SHAM
Group); or live pup weight, F(3,49)=2.18, p>0.05 (means
ranged from 4.5±0.6 g for the MPO Group to 6.0±0.2 g for'
the ASYM Group). Cannibalism was extremely rare. The
three rats that did cannibalize (a nonplacentophage with
MPO cuts, a placentophage with MFB cuts, and a
nonplacentophage with MFB cuts) ate only dead pups and
never attacked live pups.
Plaeentophagia
Delivered plaeentas. The percentages of groups of
nonplacentophages with MPO, MFB, and SHAM cuts that
ate all their delivered placentas were not significantly differ-
ent from those of placentophages with comparable cuts,
F(1,33)<1.O. However, there were significant differences