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Pharmacol Biochem Behav. Author manuscript; available in PMC 2010 March 9.
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Pharmacol Biochem Behav. 2009 March ; 92(1): 44–50. doi:10.1016/j.pbb.2008.10.008.

Difluoromethylornithine (DFMO) reduces deficits in isolation-

induced ultrasonic vocalizations and balance following neonatal
ethanol exposure in rats

Maribel A. Rubina, Kristen A. Wellmannb, Ben Lewisb, Ben J. Overgaauwb, John M.

Littletonc, and Susan Barronb,*
aDepartamento de Quimica, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil,

marubin@smail.ufsm.br
bDepartment of Psychology, University of Kentucky, Lexington, KY 40506, USA.
cCollege of Pharmacy, University of Kentucky, Lexington, KY 40506, USA, jlittlet@uky.edu
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Abstract
Neonatal ethanol (EtOH) exposure is associated with central nervous system dysfunction and
neurotoxicity in rats. Increases in polyamine levels have been implicated as one underlying
mechanism for some of EtOH’s effects on the developing brain. In this study we addressed whether
the inhibition of polyamine biosynthesis by α-difluoromethylornithine (DFMO) could reduce
behavioral deficits induced by early EtOH exposure. Male and female rat pups received ethanol (6
g/kg/day EtOH i.g.), or isocaloric maltose (control) from postnatal days (PND) 1-8. On PND 8,
animals were injected with either saline or DFMO (500 mg/kg, s.c.) immediately following the final
neonatal treatment. Subjects were tested for isolation-induced ultrasonic vocalizations (USV) on
PND 16; spontaneous activity in an open field apparatus on PND 20 and 21; and balance on PND
31. Animals exposed to EtOH neonatally displayed an increased latency to the first USV and reduced
frequencies of USV, hyperactivity and preference for the center of the open field and poorer balance
relative to controls. DFMO minimized these deficits in latency to the first USV and balance. These
data provide further support that polyamines play a role in some of the functional deficits associated
with EtOH exposure during early development and that reducing polyamine activity can improve
outcome.
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Keywords
prenatal alcohol exposure; polyamine; α-Difluoromethylornithine; isolation-induced ultrasonic
vocalizations; hyperactivity; balance

1. Introduction
Prenatal EtOH exposure disrupts central nervous system (CNS) development, leading to long-
lasting cognitive and behavioral alterations (Mattson and Riley, 1998; Roebuck et al., 1998).

© 2008 Elsevier Inc. All rights reserved.

*Corresponding author. Tel: (859) 257-5401; fax: (859) 323-1979 sbarron@uky.edu (S Barron).
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 Rubin et al. Page 2

EtOH disrupts CNS development via a variety of mechanisms, including alterations in gene
expression, cell adhesion molecule interactions, and neurotrophic support (Goodlett and Horn,
2001; West et al., 1994).
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One likely mechanism that contributes to fetal EtOH effects is NMDA receptor-mediated
excitotoxicity, which occurs during periods of EtOH withdrawal (Hoffman and Tabakoff,
1994; Thomas and Riley, 1998). Consistent with this hypothesis, blocking NMDA receptors
with the noncompetitive antagonist MK-801, during withdrawal, attenuates some of the
adverse effects of EtOH on behavioral and brain development in both in vivo rat models of
early developmental EtOH exposure (Thomas et al., 1997) and in vitro organotypic
hippocampal cultures (Prendergast et al., 2000). Moreover, the beneficial effects of MK-801
are time-dependent (Thomas et al., 2001), indicating that NMDA receptor blockade is only
effective during the withdrawal phase.

NMDA receptors comprise an assembly of subunits (an NR1 subunit plus at least one type of
NR2 subunit) with a number of modulatory sites, including modulatory polyamine binding
sites, which are in high levels on the NR2B subunit (Williams, 1994; Williams et al., 1994).
Eliprodil, inhibits NMDA receptor activity by interacting allosterically with the polyamine
modulatory site on the NR2B NMDA receptor and if administered during EtOH withdrawal,
reduces the severity of learning deficits associated with developmental EtOH exposure
(Thomas et al., 2004a). There has been interest in the potential role of polyamines in the
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deleterious effects of EtOH for some time (Sessa et al., 1987; Shibley et al., 1995). Recent in
vitro studies provide further support for the role of polyamines in EtOH withdrawal-induced
neurotoxicity, since not only polyamine binding site antagonists, but also polyamine synthesis
inhibitors protect against EtOH withdrawal-induced neurotoxicity (Gibson et al., 2003;
Littleton et al., 2001). Accordingly, polyamines and glutamate are released during EtOH
withdrawal (Gibson et al., 2003), providing additional evidence for a role of polyamines in
EtOH withdrawal-induced neurotoxicity. However, this is the first study, to the best of our
knowledge, that has addressed whether inhibition of polyamine biosynthesis could reduce
behavioral deficits induced by early EtOH exposure. In this study, we examined whether the
administration of DFMO, which inhibits ornithine decarboxylase (ODC), the rate-limiting step
in the synthesis of polyamines, reduces short and more long-term deficits induced by EtOH
exposure from PND 1-8.

2- Materials and Methods

2.1. Animals
Male and female Sprague-Dawley rats were bred in the Psychology Department Animal
Facility at the University of Kentucky. Birth was considered postnatal day (PND) 0. On PND
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1, litters were weighed and randomly culled to 10 pups, keeping 5 males and 5 females
whenever possible. The animals were maintained on a 12-h light/dark cycle (lights on at 7:00
a.m.) with ad libitum access to water and standard laboratory rat chow in a nursery that was
temperature and humidity controlled. All experimental procedures were conducted between
9:00 and 16:00h. All protocols were approved by the Institutional Animal Care and Use
Committee at the University of Kentucky and are in compliance with the National Institutes
of Health Guide for Care and Use of Laboratory Animals.

2.2. Neonatal drug administration

On PND 1, rat pups were randomly assigned to each of the six treatment groups (when possible)
in such a way that each litter contributed no more than one animal for each treatment group to
preclude potential litter effects (Abbey and Howard, 1973). From PND 1 to PND 8, one male
and one female from each litter were given 3 g/kg EtOH (in a milk formula (West et al.,

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1984)) or isocaloric maltose (isocaloric control group, milk formula plus maltose) by gavage
(0.0278 ml/g bw, bid, at 10:00 and 14:00) with polyethylene PE-10 tubing (Clay Adams), as
previously described (Goodlett et al., 1998) resulting in 6 g/kg/day of EtOH. A non-intubated
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control group was also included. This neonatal EtOH exposure model is used to study a period
of CNS development that overlaps the 3rd trimester “brain growth spurt” observed in human
pregnancy (Dobbing and Sands, 1979).

On PND 8, offspring were also injected with either 0.9% NaCl (saline, 5 ml/kg, s.c.) or DFMO
(500 mg/kg, s.c.) immediately after the last gavage. DFMO was administered immediately
after the last gavage because a single injection of 500 mg/kg DFMO markedly reduces
polyamine levels in neonatal rat brain for at least 24 hr (Slotkin et al., 1982) and thus polyamines
would be suppressed during withdrawal at times that have previously been shown to be the
most responsive to blockade of GLU or NMDAR during EtOH withdrawal (Thomas et al.,
2001; 2004a). This dose has also been shown to reduce the severity of EtOH withdrawal
behaviors (Davidson and Wilce, 1998). DFMO was administered only on a single day because
of concern regarding the important role that polyamines play in CNS development and because
repeated injections of DFMO itself can cause reductions in cerebellar size (Schweitzer et al.,
1989; Sparapani et al., 1996). This resulted in six treatments groups: Intubated Control/Saline,
Intubated Control/DFMO, Intubated EtOH /Saline, Intubated EtOH /DFMO and Non-
intubated Control/Saline and Non-intubated Control/ DFMO. The n’s for each treatment
condition are presented in the data figures. Approximately 16 – 20 dams and their litters were
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used for this series of studies.

2.3. Isolation-induced Ultrasonic Vocalization (USV) testing

USVs were examined according to published procedures (Barron and Gilbertson, 2005). In
brief, an ultrasonic bat detector (Ultra Sound Advice Model #S-25, UK-
http://www.ultrasoundadvice.co.uk) set at 40 kHz with a condenser microphone (SM-1) set
21.5 cm above the test cage floor was used. The output was recorded on a SONY #WM-D8C
Cassette Recorder using low noise cassette tapes. Testing was conducted on PND 16 since pilot
data from our laboratory has shown that this age is sensitive to neonatal EtOH’s effects on
isolation induced USVs.

On PND 15, each pup was briefly removed from the litter and tail-marked in random order (for
neonatal treatment condition and sex) with a permanent marker to keep the experimenter blind
to treatment condition. On PND 16, the dam was removed from the home cage, placed in a
holding cage and returned to the cage rack. The litter was maintained with conspecifics in the
home cage placed on a heating pad. White noise was generated via small fans to mask
extraneous environmental noises or noises from other littermates. Each pup was individually
tested by placing the pup in the lower right corner of the test cage (21 cm × 11 cm) with clean
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pine bedding for a 6 min test session. At the conclusion of testing, the pup was removed from
the test chamber and weighed. Once all of the subjects in the litter were tested, the dam was
returned to the litter. Audiotapes were subsequently played back and the latency to the first
vocalization and the number of USVs were recorded. Two experimenters blind to treatment
condition scored the USVs and the reliability across experimenters was at least 90%.

2.4. Open field

Beginning on PND 20, animals were individually tested in a round open field apparatus (55
cm in diameter) between the hours of 1000 and 1400 h during the light cycle. Pre-weanling
animals were used in this study because previous reports have shown that neonatal EtOH
exposure induces hyperactivity at this age (Gilbertson and Barron, 2005; Kelly et al., 1987;
Melcer et al., 1994). Pups were separated from their dam and put on heating pads in their home
cage until all pups in the litter were tested. Each subject was individually placed in a holding

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cage and brought into the test room for 10 min habituation prior to placement in the open field.
Locomotor activity was measured by a Polytracker Video Imaging System (San Diego
Instruments) interfaced with an IBM computer for 20 min daily for two consecutive days (PND
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20 and 21). Testing was conducted in a darkened room with fans to provide white noise. The
dependent variables recorded included total distance traveled, and the percent of distance
traveled and percent of time spent in the center (31.8 cm in diameter) of the open field. The
open field apparatus was cleaned with isopropyl alcohol before and after each subject. Body
weights were taken one day prior to testing (PND 19). After open-field testing, offspring were
weaned on PND 21 and housed with 1 – 2 same sex conspecifics.

2.5. Balance test

The balance apparatus consisted of a single elevated dowel rod (120 cm long, 1.85 cm
diameter), with a darkened escape box (21 × 10 × 17 cm) on one end. The rod was raised (60
cm) above the ground, which was well padded in case of falls. The balance test was conducted
on PND 31 and animals received three trials. Each animal was habituated to both the testing
room and escape box for 1 min each on PND 31. This age was also chosen based on previous
findings from our lab (Lewis et al., 2007a). During the first trial, the animal was placed gently
on the rod, 10 cm from the escape box. Upon successfully reaching the escape box, the animal
was allowed to remain in the box for 10 sec, and was then returned to its home cage. If the
animal did not successfully reach the escape box (either fell or more often swung from the
rod), it was retrieved and placed in the escape box for 10 sec, before being returned to the home
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cage. If the subject successfully traversed the rod, the distance on the next trial was increased
by 13 cm. Each trial was separated by a 30 sec intertrial interval. Subjects that were
unsuccessful were retested at the same distance on the rod. The dowel rod and the escape box
were cleaned with 30% isopropyl alcohol before and after each rat occupied it. The dependent
measure was the distance successfully achieved on each trial (if an animal fell on any trial, the
last successfully completed distance was recorded for that trial). Body weights were recorded
on the day before testing (PND 30).

2.6 Blood ethanol assay

Pups from 14 additional litters were intubated twice daily on PNDs 1–8 for measurement of
blood EtOH concentrations (BECs) to assess whether DFMO had effects on EtOH metabolism.
Blood was collected after the second EtOH intubation on PND 8 by making a 1 mm cut at the
tip of the subject’s tail and collecting 20 μl of blood. The BEC curve was established by
collecting samples at 30, 60, 120, 240, 480 and 600 min (and 24h) following EtOH
administration. In order to reduce stress, each subject was only sampled three times with one
male and one female represented in each time point. These subjects were not used for further
behavioral study. Plasma was separated and frozen at −70° F. BECs were assayed using an
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Analox AM 1 Analyzer (Analox Instruments).

2.7. Statistical analysis

The data were analyzed using ANOVA followed by post hoc analyses (Newman-Keuls test or
F test for simple effect analyses) with between group factors including neonatal treatment
group, sex, and repeated measures as warranted. In addition, to better directly examine the
interaction of EtOH and DFMO, additional ANOVAs were conducted using EtOH and DFMO
as grouping factors. For these analyses, the intubated control and the nonintubated control
groups were combined into a single control group as separate ANOVAs did not reveal any
differences between these control groups in any of the behavioral measures or in body weight.
For ease of presentation, the data was collapsed across sex since there was no main effect or
interaction with sex. There was some variation in ns across experiments due to experimenter
error, equipment failure or computer malfunction although this was equally distributed across

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treatment condition. The n/treatment group in each experiment is presented in its respective
figure with the n’s for controls representing the pooled control group.
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3. Results
3.1. Isolation-induced USVs
Fig. 1A shows the effects of DFMO and neonatal EtOH exposure on the latency to the first
vocalization. Statistical analysis (two-way ANOVA) revealed that the EtOH exposed offspring
took longer to vocalize and the administration of DFMO minimized this effect (significant
EtOH × DFMO interaction: F(1,98)=4.20, p<0.05).

Fig. 1B shows the effect of DFMO and neonatal EtOH exposure on the frequency of USVs.
Statistical analysis (two-way ANOVA with repeated measures ) revealed a main effect of EtOH
[F(1,98)=13.05, p<0.05] although there was no interaction with DFMO. Thus, neonatal EtOH
exposure reduced the frequency of USVs across the test session relative to controls and DFMO
did not eliminate this deficit.

3.2. Open field

Fig. 2 shows the effect of neonatal DFMO and EtOH exposure on locomotor activity. The 2 ×
2 ANOVA revealed a main effect of neonatal EtOH exposure [F(1,93)=26.15, p<0.001] and
day [F(1,93)=15.05, p<0.001]. Animals exposed to neonatal EtOH were more active (i.e.
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increased distance traveled) on both days of testing relative to animals treated with DFMO
alone or controls. The addition of DFMO to the EtOH exposed group did not reduce this
hyperactivity. The main effect of day was due to a reduction in locomotor activity across the
two days of testing (habituation). This was displayed by all treatment groups.

Fig. 3 shows the effect of neonatal DFMO and EtOH exposure on the percent distance traveled
in the center of the open field. Animals treated with EtOH neonatally traveled proportionally
more distance (Fig 3) and spent proportionally more time in the center of the open field relative
to control animals. DFMO did not alter or eliminate this EtOH effect. The ANOVA revealed
a main effect of EtOH for distance traveled [F(1,93)=13.16, p<0.001] and the amount of time
spent in the center [F(1,93)=8.93; p<0.005].

3.3. Balance test

Fig. 4 shows the effect of neonatal DFMO and EtOH exposure on performance on the single
dowel task. Statistical analysis (three-way ANOVA) revealed a significant EtOH by DFMO
by trial interaction [F(2,250)=3.45, p<0.05]. Post hoc analyses revealed that neonatal EtOH
exposure impaired performance as measured by a reduction in the distance successfully
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traversed across trials compared to controls [F(2,250)=14.49, p<0.01]. DFMO administration

on PND 8 minimized this effect of EtOH exposure by the third trial [F(1,125)=5.70, p<0.05;
univariate two-way ANOVA followed by Student-Newman-Keuls test].

3.4. Body weights

Statistical analysis of body weight during neonatal treatment (i.e. from PND 1 to 8) with a
three-way ANOVA, with neonatal treatment, DFMO and gender as fixed factors and day as a
repeated measure (within-subject factor) revealed a significant neonatal treatment by day
interaction [F(14,854)=39.70, p<0.001]. DFMO was included as a factor (although DFMO
was not administered until after pups were weighed on PND 8) to ensure that there were no
unintended baseline differences in body weight in subjects designated to receive DFMO.
Subsequent univariate ANOVAs showed that pups exposed to EtOH weighed less than controls
from PND 2 onwards and the controls did not differ from each other (see Fig 5). In addition,

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statistical analysis revealed that males weighed more than females regardless of neonatal
treatment [F(1,122)=5.16, p<0.05].
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The body weights recorded prior to or after behavioral testing are presented in Table 1. There
were no differences between the non-treated and intubated/SAL control groups nor the DFMO
controls (non-treated and intubated) across any of the ages examined, so the data were collapsed
for the control groups (as was done for the behavioral analyses).

Body weights assessed on the day of USV testing (PND 16) revealed a main effect of both
EtOH [F(1,87)=50.65, p<0.0001] and DFMO [F(1,87)=4.25, p<0.05] (see Table 1). These data
indicate that neonatal treatment with EtOH or with DFMO resulted in reductions in body weight
relative to non exposed offspring. There was no EtOH × DFMO interaction.

Body weights recorded on the day before open-field testing (PND 19) revealed a main effect
of neonatal EtOH exposure [F(1,89)=59.89, p<0.0001] and sex [F(1,89)=7.79, p<0.01] (see
Table 1). The EtOH exposed offspring still had reduced weights relative to controls.
Additionally, as predicted, males weighed more than females.

Finally, this pattern was consistent when body weights were recorded the day before testing
on the single dowel test (PND 30). The ANOVA showed with a main effect of both neonatal
EtOH exposure [F(1,125)=34.51, p<0.0001] and sex [F(1,125)=28.96, p<0.0001] (see Table
1). Thus, neonatal EtOH exposure produced a persistent reduction in body weight relative to
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controls.

3.5. Blood ethanol levels

Blood EtOH concentrations (BECs) measured on PND 8 are presented in Figure 6. The addition
of DFMO did not alter BEC pharmacokinetics at any of the time points examined. The ANOVA
on these data revealed no EtOH × DFMO interaction.

4. Discussion
In this study we showed that neonatal exposure to EtOH from PND 1 to 8 produced significant
behavioral alterations in young rats, some of which were reduced or minimized by the
administration of DFMO on PND 8. The PND 1 to 8 is a period of brain development marked
by high sensitivity to EtOH (Thomas et al., 1997), to NMDA receptor-mediated excitotoxicity
(Ikonomidou et al., 2000), and to polyamines (Slotkin et al., 2003). This is also a period that
occurs postnatally in the rat, but overlaps a portion of the third trimester of human pregnancy
in terms of CNS development (Dobbing and Sands, 1979). The findings from this study also
showed that there were no differences in blood EtOH concentrations as a consequence of
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DFMO treatment ruling out this alternative interpretation for DFMO’s effects. The behavioral
impairments associated with neonatal EtOH exposure observed in the current study included
increased latency to the first USV and reduced frequency of USVs at PND 16; increased
locomotion and preference for the center of an open field at PND 20-21 and poorer performance
in a balance paradigm at PND 31. The administration of DFMO eliminated the EtOH -related
increase in latency to the first USV at PND 16 and improved balance performance on PND 31.

DFMO blocks ODC, the rate limiting step for polyamine biosynthesis. DFMO is a fairly small
lipid soluble molecule that crosses the blood brain barrier and inactivates ODC molecules semi-
permanently. While it reduces the capacity for polyamine synthesis quickly (Slotkin et al.,
1982), it does not really alter “resting” levels of polyamines. DFMO has a significant effect
when polyamine synthesis by ODC is increased such as during chronic ethanol exposure or
during ethanol withdrawal (Davidson and Wilce, 1998) and the blunted response lasts until
new ODC can be synthesized (maybe several days), providing “protection” during EtOH

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withdrawal. These results provide support for the role of polyamines in some of the behavioral
teratogenic effects of neonatal EtOH exposure.
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There is a considerable body of evidence suggesting that polyamines play a major role in EtOH
withdrawal-induced neurotoxicity. Data from in vitro studies have shown that polyamine
synthesis is increased during EtOH withdrawal and that inhibition of polyamine biosynthesis
via DFMO decreased hippocampal neuronal death caused by EtOH withdrawal (Gibson et al.,
2003) and reduced EtOH-induced protein carbonylation (Mello et al., 2007). In vivo studies
have shown that chronic EtOH exposure increased hippocampal ODC activity and this increase
was positively correlated with physical indicators of dependence. DFMO (at the same dose
used in the current study) significantly reduced these physical withdrawal signs (Davidson and
Wilce, 1998) however it should be noted that we did not examine physical withdrawal signs
in the current study.

The protective action of DFMO in the current study suggests that inhibition of polyamine
synthesis may also reduce the damage associated with neonatal EtOH exposure and/or
withdrawal in vivo. Of particular note, functional improvements were observed with only a
single injection of DFMO on PND 8. A number of studies clearly suggest that the cerebellum
is more sensitive to EtOH during the first postnatal week relative to the 2nd (Lewis et al.,
2007a; Thomas et al., 1998; Goodlett et al., 1996) and the fact that DFMO was able to reduce
these deficits even when administered on PND 8 is extremely interesting. It is important to
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note, however, that chronic DFMO has its own deleterious effects on the developing brain
(Slotkin et al., 2000; Bartolome et al., 1985).

The cerebellum plays a key role in balance and coordination. The cerebellum also appears to
be particularly sensitive to prenatal/neonatal EtOH exposure. In clinical studies, balance and
coordination deficits have been reported in children exposed to EtOH prenatally (Kyllerman
et al., 1985; Streissguth et al., 1980) and these findings have been substantiated by functional
and structural imaging studies in which deficits have been observed in children with FAS
(Riley and McGee, 2005; Riley et al., 2004; Roebuck et al., 1998). Rodent models have also
shown that rat cerebellum appears particularly sensitive to 3rd trimester EtOH exposure with
both behavioral and neuroanatomical deficits reported (Goodlett et al., 1991; Green et al.,
2000; Klintsova et al., 1998; Klintsova et al., 2000; Thomas and Riley, 1998).

In rats, the first neonatal week appears to be particularly sensitive to EtOH’s effects and this
coincides with high expression of cerebellar NR2B subunits (Zhong et al., 1995). As stated in
the introduction, the NR2B subunit displays twice the sensitivity to EtOH as other subunits
(NR2C or NR2D) (Allgaier, 2002; Kuner et al., 1993; Masood et al., 1994; Mirshahi and
Woodward, 1995; Sucher et al., 1996) and the NR2B subtype is also particularly sensitive to
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polyamine manipulations (Williams et al., 1994). Thus, EtOH exposure on PND 1-8 may have
its effect on cerebellar function and structure, at least in part, due to the higher proportion of
NR2B subtypes and their greater sensitivity to EtOH and to polyamines. Reducing polyamine
levels via DFMO and hence reducing NMDAR activity during EtOH withdrawal could help
explain the improved balance performance by EtOH/DFMO exposed offspring. This dose of
DFMO also has been shown to reduce the severity of EtOH l withdrawal behaviors (Davidson
and Wilce, 1998). Additional support for our hypothesis includes findings that show that
agmatine, which can block the polyamine site on the NMDAR (Lewis et al., 2007a) and CP
101,606 and eliprodil, both of which are NR2BR antagonists (Lewis et al., 2007b; Thomas et
al., 2004a) also reduce behavioral deficits including balance following neonatal EtOH
exposure.

The effects of DFMO on reducing EtOH’s effects on isolation induced ultrasonic vocalizations
are more complex. DFMO eliminated the EtOH-related deficit in latency to USV but had no

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effect on the frequency of USVs. Isolation induced USVs have been studied to assess anxiolytic
agents, i.e. used as a model of stress (Iijima and Chaki, 2005) and have frequently been used
to study the role of environmental factors and/or neurotoxicants that influence this species-
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adaptive response (Adams et al., 1983; Branchi et al., 2001). Many neurotransmitters/
neurochemicals appear to play a role in USVs, including benzodiazepines (Carden and Hofer,
1990a; Insel et al., 1986), opioids (Carden and Hofer, 1991, 1990b), serotonin (Albinsson et
al., 1994a; Albinsson et al., 1994b; Hard and Engel, 1988; Winslow and Insel, 1991), dopamine
(Dastur et al., 1999) and corticotropin releasing factor (Hennessy et al., 1992; Insel and
Harbaugh, 1989). Isolation induced USVs elicit a variety of forms of maternal attention
(Brouette-Lahlou et al., 1992; Fernandez et al., 1983) and disruption in the normal response to
isolation could have significant consequences for maternal/infant interactions. We have
previously suggested that this deficit displayed by EtOH exposed offspring could have long-
term consequences for the offspring (Barron and Gilbertson, 2005; Barron et al., 2000) and it
is well known that impairments in maternal/offspring relationships have long-term effects on
social behaviors, neuroendocrine development (Liu et al., 1997; Moore et al., 1997) and
learning (Barbazanges et al., 1996; Levy et al., 2003). While DFMO did not eliminate EtOH
l-induced deficits, it did at least ameliorate the delayed latency to USV.

Neonatal EtOH exposure was also associated with hyperactivity and DFMO administered on
PND 8 did not eliminate this deficit. Hyperactivity following neonatal EtOH exposure is a
frequently reported developmental effect of EtOH on behavior (Gilbertson and Barron, 2005;
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Saglam et al., 2006; Slawecki et al., 2004; Thomas et al., 2001). While the specific mechanisms
by which EtOH causes hyperactivity are also not well understood, it has been argued that these
deficits, at least in rodent models, may be due to hippocampal abnormalities resulting in
perseveration and habituation deficits associated with prenatal/neonatal EtOH exposure (Riley
et al., 1986).

In addition to hyperactivity, the EtOH -exposed offspring displayed an increased preference

for the center of the open field, as measured by increased distance traveled and increased
proportion of time spent in the center of the chamber relative to control animals. Rats typically
display thigmotaxis and spend more time near the perimeter walls of a test chamber rather than
entering or crossing into the center. Increased time spent in the center could simply be another
indicator of hyperactivity or could be a reduction in the normal species-typical thigmotaxic
response displayed by rats when placed in a novel open-field which might be interpreted as
reduced anxiety about entering the center of the chamber. We have previously shown that a
similar pattern in males treated with EtOH from PND 1 to 7 who also traveled greater distance
in the center than controls on PND 19-21 in a traditional square open-field chamber (Gilbertson
and Barron, 2005), but again, this paradigm does not allow us to determine if these changes in
behavior are due to hyperactivity with a failure to inhibit entries into the center or some change
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in anxiety response to the open-field.

Clearly, DFMO did not reduce or eliminate all of the effects of neonatal EtOH exposure
reported in this series of studies. This was not surprising since prenatal and neonatal EtOH
exposure can cause a wide range of effects on CNS and neurotransmitter systems (Goodlett
and Horn, 2001; Goodlett et al., 2005; Guerri, 1998; 2002). It is extremely unlikely that all of
the functional deficits displayed by offspring exposed to EtOH are mediated by NMDAR and
polyamine overactivity. Other studies in which reductions or elimination of functional deficits
following early EtOH exposure provide further support for this argument as well. For example,
neonatal choline supplement reduced the effects of neonatal EtOH exposure on activity and
spatial learning (Thomas et al., 2004b) but had little or no effect on balance impairments
(Thomas et al., 2004c).

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Neonatal EtOH exposure was associated with reduced body weights and this persisted through
PND 30. It is unlikely that this reduction in body weight alone contributed to the deficits
observed in the current study since the DFMO/ EtOH offspring had similar body weights yet
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performance was improved on balance and latency to the first USV. Still, EtOH did produce
a persistent reduction in body weight. DFMO alone may also have exerted a mild effect on
body weight with a slight but statistically significant reduction in body weight in offspring on
PND 16 that was no longer observed by PND 19 (the next time that pups were weighed).
Previous studies have documented that more chronic neonatal DFMO treatment can reduce
body weight (Slotkin et al., 1982; Slotkin and Bartolome, 1986) but the single injection used
in this study produced a transient effect at best.

In summary, DFMO administered following chronic neonatal EtOH exposure reversed some
of the behavioral consequences of neonatal EtOH exposure in our rodent model. These findings
suggest that compounds that reduce polyamine levels during EtOH withdrawal eliminate some
of the deficits associated with neonatal EtOH exposure. It is important to note that this approach
is somewhat complicated considering the important role that polyamines play in CNS
development (Jasper et al., 1982; Slotkin and Bartolome, 1986) and it may be that the timing
of polyamine suppression in relation to EtOH withdrawal is critical. Clearly, further work is
needed to assess this potential treatment approach.

DFMO is currently used clinically as an antineoplastic therapy (due to the role of polyamines
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in cell growth) (Casero et al., 2005; Huang et al., 2005) and is also used in treatment of some
forms of trypanosomiasis (sleeping sickness) (Chappuis et al., 2005; McCann et al., 1981)
although chronic administration of DFMO can have adverse side effects (Nie et al., 2005).
Additional studies are clearly needed to gauge the potential usefulness of DFMO and other
polyaminergic agents in reducing fetal alcohol effects.

Acknowledgments
MAR is recipients of CNPq (200016/2005-9) fellowship. Work supported by NIH grants to SB (AA-014032) and to
JML (AA-12600; AA-01388).

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Figure 1.
DFMO minimized the increase in latency to the first vocalization as a result of neonatal ethanol
(EtOH) exposure when offspring were tested at PND 16 (A), but had no effect on the EtOH -
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related decrease in the number of USVs (B). Data presented are mean (collapsed across sex)
+ SEM. The control group represents the pooled nontreated and intubated controls since these
groups did not differ from each other and this pooled control was used in the 2 × 2 factorial
design. The n’s per treatment condition are presented in the parentheses above each bar. *
differs from all other treatment groups; # differs from controls (p’s< 0.05).

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 Rubin et al. Page 15
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Figure 2.
Neonatal EtOH increased the total distance traveled in the open field on PND 20-21. Data
presented are mean (collapsed across sex) ± SEM. The control group represents the pooled
nontreated and intubated controls since these groups did not differ from each other and this
pooled control was used in the 2 × 2 factorial design. The n’s per treatment condition are
presented in the parentheses alongside the figure legends. * differs from EtOH subjects (p<
0.05).
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 Rubin et al. Page 16
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Figure 3.
Neonatal EtOH exposure increased the percent of distance traveled (A) and time spent (B) in
the center 50% of the open field on PND 20-21. Data presented are mean ± SEM. The control
group represents the pooled nontreated and intubated controls since these groups did not differ
from each other and this control was used in the 2 × 2 factorial design. The n’s per treatment
condition are presented in the parentheses alongside the figure legends in Figure 2.
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 Rubin et al. Page 17
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Figure 4.
DFMO on PND 8 reduced the deleterious effect of neonatal EtOH exposure on the total distance
achieved in the balance test at PND 31. Data presented are mean (collapsed across sex) ± SEM.
The control group represents the pooled nontreated and intubated controls since these groups
did not differ from each other and this pooled control was used in the 2 × 2 factorial design.
The n’s per treatment condition are presented in the parentheses alongside the figure legends.
* differs from all other treatment groups.
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 Rubin et al. Page 18
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Figure 5.
Neonatal EtOH administration was associated with reduced body weights relative to controls
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beginning on PND 2 and continuing through PND 8. Data presented are mean (collapsed across
sex) ± SEM. The control group represents the pooled nontreated and intubated controls since
these groups did not differ from each other and this pooled control was used in the 2 × 2 factorial
design. The n’s per treatment condition are presented in the parentheses alongside the figure
legends. The EtOH group differed from controls from PND 2 through PND 8 (p’s <0.05).
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 Rubin et al. Page 19
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Figure 6.
Blood EtOH levels did not differ between DFMO-treated and saline control rats following
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EtOH intubation. EtOH (3 g/kg) was administered twice daily from PND 1-8. Blood levels
were assayed on PND 8.
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Table 1
Mean body weight (in g) ± S.E.M. as a function of neonatal treatment (PND 1-8) and sex.

Group PND 16 PND 19 PND 30

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MALE FEMALE MALE FEMALE MALE FEMALE

Control/SAL 41.5 ± 1.2 40.2 ± 1.1 54.6 ± 1.3 51.5 ± 1.2 104.9 ± 2.4 94.6 ± 2.2
Control/DFMO 38.6 ± 1.5 38.1 ± 1.3 53.2 ± 1.5 50.2 ± 1.4 103.8 ± 2.6 93.9 ± 2.3

EtOH /SAL 33.4 ± 2.0* 32.4 ± 1.5* 46.4 ± 1.7* 41.3 ± 1.7* 93.2 ± 3.2* 84.4 ± 2.7*

EtOH / DFMO 30.7 ± 1.7* 31.2 ± 1.6* 44.4 ± 1.8* 41.3 ± 1.7* 93.5 ± 3.0* 80.4 ± 3.3*

SAL is Saline. N’s are presented in Figures 1-4.

*
p < 0.05 relative to same-aged controls

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