HYPOTHALAMIC CUTS AND MATERNAL BEHAVIOR
among the four surgical groups, F(3,49)=7.25, p<0.0L
Ninety percent of the rats in the SHAM Group ate all their
placentas, but only 33% of each of the knife-cut groups ate all
their placentas. Pairwise comparisons indicated that there
were no significant differences among the MPO, MFB, and
ASYM Groups, but each of these groups was significantly
different from the SHAM Group.
Donor placentas. The percentages of groups of
nonplacentophages with MPO, MFB, and SHAM cuts that
ate donor placenta 1 hr after parturition were not signifi-
cantly different from those of placentophages with com-
parable cuts, F(l,33)<1.0. When data from placentophages
and nonplacentophages were combined, there were no signif-
icant differences among the four surgical groups,
F(3,49)<1.0. The percentage of each group that ate donor
placenta was: MPO: 58%; MFB: 67%; ASYM: 88%; SHAM:
57%.
Pup-Directed Maternal Behavior and Nestbuilding
At the end of each of the 11 maternal behavior and
nestbuilding tests, each rat was scored as having begun (1) or
not having begun (O) to display (a) retrieving of all four pups,
(b) crouching over one or more pups, (c) pup-licking, and (d)
nestbuilding. For each of these dependent measures, the re-
sulting set of dichotomous data was analyzed using a
1-within, 1-between ANOVA [26] with Locus of Knife Cut
as the between factor and Test as the within factor.
Retrieving. Figure 1 shows the cumulative percentage of
rats in each group that retrieved all four foster pups. There
were significant differences among the groups on Test 1,
F(3,l 12)= 17.72,p<0.01, in that the percentages of the MPO,
MFB, and ASYM Groups that retrieved during this test were
significantly lower than that of the SHAM Group, but were
not different from each other. Over the course of testing,
there was a significant increase in the percentage of rats
retrieving in the MFB Group, F(10,490)=15.48, p<0.01, and
in the ASYM Group, F(10,490)=7.18, p<0.01. That is, rats
with MFB or ASYM cuts showed a delayed onset of retriev-
ing; at least half of each of these groups had retrieved pups
by Test 11 on Day 5 postpartum.
Crouching. Figure 1 shows the cumulative percentage of
rats in each group that adopted a crouching posture over one
or more pups. There were significant differences among the
groups on Test 1, F(3,101)= 11.39, p<0.01. The percentages
of rats in the MPO, MFB, and ASYM Groups that crouched
on this test were significantly lower than that of the SHAM
Group but were not different from each other. However,
over the course of testing, there were significant increases in
the percentage of rats crouching over pups for each of the
three knife-cut groups, MPO: F( 10,490)= 10.79, p<0.01;
MFB: F(10,490)=8.13, p<0.01; ASYM: F(10,490)=9.18,
p<0.01. By Test 11, there were no significant differences
among the four groups, F(3,101)=2.19, p>0.05.
Pup-licking. Figure 1 shows the cumulative percentage of
rats in each group that licked pups. The effects of cuts on
pup-licking were similar to the effects on crouching. There
were significant differences among the groups on Test 1,
F(3,119)= 13.53, p<0.01. The percentages of rats in the three
knife-cut groups that licked pups during this test were signif-
icantly lower than that of the SHAM Group but were not
different from each other. Over the course of testing, how-
ever, there were significant increases in the percentage of
rats licking pups in each of the three knife-cut groups, MPO:
F(10,490)= 17.02, p<0.01; MFB: F(10,490)= 14.48, p<0.01;
633
FIG. 1. Cumulative percentages of groups of primiparous rats, after
knife-cut surgery, that displayed retrieving, crouching, pup-licking
and nestbuilding across tests.
ASYM: F(10,490)=8.04, p<0.05. By Test 11, there were no
significant differences among the groups, F(3,119)<L0.
Nestbuilding. Figure 1 shows the cumulative percentage
of rats in each group that built nests. There were significant
differences among the groups on Test 1, F(3,l 11)= 11.81,
p<0.01. The percentages of rats in the MPO, MFB, and
ASYM Groups that built nests on this test were significantly
lower than that of the SHAM Group but were not different
from each other. The percentage of rats that built nests did
not increase over testing for the MPO Group,
F(10,490)=1.13, p>0.05, nor for the MFB Group,
F( 10,490)= 1.70, p>0.05, but did increase for the ASYM
Group, F(10,490)= 10.70, p<0.01. MPO or MFB cuts elimi-
nated nestbuilding for the entire 11-day test period, but
ASYM cuts only delayed the onset of nestbuilding; half of
this group had built nests by Test 11 on postpartum Day 5.
Test for Hyperphagia. Rats with MFB cuts were hyper-
phagic on all 10 days of exposure to the high-fat diet.
They ate an average of 9.5% of their body weight on each
day of testing, compared with 6.0%, 6.5% and 5.7% for
rats with MPO, ASYM, and SHAM cuts, respectively,
F(3,49)=34.92, p<0.01. For each rat, body weight on Days
1-10 was calculated as percentage of body weight on Day 0.
Significant differences among the groups were apparent as
early as Day 2, F(3,77)=3.56, p<0.05. By Day 10, the MFB
rats weighed almost 140% of the Day 0 baseline, whereas the
other groups averaged 109% of baseline.
Histological Analysis
Examination of brain sections revealed that the MPO cuts
were similar to those described by Numan [39]. There was
little variability in the extent and location of MPO cuts. They
were bilaterally symmetrically located between 1.3 and 1.5
mm lateral to midline, just medial to the supraoptic nuclei
[47]. In 10 of the 12 rats, the cuts began at the rostral end of
the MPO (A 7.8-8.2) and extended caudally into the anterior