Journal of Behavioral and Brain Science, 2011, 1, 1-5
doi:10.4236/jbbs.2011.11001 Published Online February 2011 (http://www.SciRP.org/journal/jbbs)
Effect of Ethanol Deprivation and Re-Exposure on the
Ethanol Drinking Behaviour of the High-Alcohol-Drinker
(UChB) Rats
Lutske Tampier, Maria Elena Quintanilla
Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine,
University of Chile, Santiago, Chile
Received January 4, 2011; revised February 20, 2011; accepted February 22 , 20 11
Abstract
Alcohol addiction constitutes a major health problem in the general population, it is a complex pathology
characterized by the development of tolerance, physical dependence and compulsive ethanol-seeking behav-
iour that often manifests as a chronic relapsing syndrome. 0ne of the major concerns in the treatment of al-
cohol-dependent patients is the prevention of relapse during periods of abstinence. The alcohol deprivation
effect (ADE) is defined as a temporary increase in the voluntary intake of ethanol when it is reinstated after a
period of alcohol deprivation and has been used as an animal model of relapse-like drinking. ADE can be
used to evaluate the efficacy of possible pharmacological agents to prevent relapse drinking. The current
study was undertaken to examine whether the high-alcohol-drinker UChB rats would display an ADE. Rats
were given either continuous or periodic concurrent access to 10%, 20% (vol/vol) of ethanol across depriva-
tion cycles. UChB rats consuming ethanol voluntarily for two months, exhibit a robust ADE after a single
deprivation period of two weeks. The increased alcohol intake during the early days of re-exposure, follow-
ing a withdrawal phase, is attributed to a shift in preference towards the higher concentration of ethanol that
might reflect an increase in craving for alcohol. Since an ADE is also observed in UChB rats, make this line
of rats selectively bred for their high voluntary ethanol consumption, a useful model for study the efficacy of
pharmacological agents for the treatment of relapse of alcohol consumption.
Keywords: Alcohol Intake, Alcohol Deprivation, Alcohol Drinking Rats, UChB Rats
1. Introduction
Addiction can be best defined as the loss of control over
drug use. I t is caused by the action of a drug of abuse and
generally requires repeated drug exposure. One of the
drugs more abused is alcohol. Alcohol addiction (Alco-
holism) constitutes a major health problem in th e general
population, it is a complex pathology characterized by
the development of tolerance, physical dependence and
compulsive ethanol-seeking behaviour that often mani-
fests as a chronic relapsing syndrome. As a matter of fact,
one of the major concerns in the treatment of alco-
hol-depe ndent patients is the pre vention of rela pse during
periods of abstinence.
According to Spanagel and Hölter (1999) [1], alcohol
drinking over a long period of time can be separated into
three stages. First, the initiation or acquisition of alcohol
drinking, followed by a second stage of controlled alco-
hol-drinking behaviour and eventually a third stage
where uncontrolled alcohol-drinking behaviour occurs,
leading to the development of dependence, which has
been characterized as an progressive dysregulation of
brain reward and stress circuits [2,3]. Although these
various stages of alcohol drinking occur in humans, it is
not clear whether those transitions in alcohol drinking
from one stage to another can also be observed in all
animals with a high preference an d a high daily intake of
alcohol Various approaches have been used to evaluate
the occurrence of addictive behaviour in laboratory ani-
mals; most of them based on changes in the amount of
alcohol intake following a period of abstinence and a
shift of preference towards higher concentration of etha-
nol solutions [1]. The alcohol deprivation effect (ADE)
has been proposed as a model of “loss of control” and

2 L. TAMPIER ET AL.
“relapse-like” drinking [4,5] and that can be used to
evaluate the efficacy of possible pharmacological agents
to prevent relapse drinking. ADE is defined as a tempo-
rary increase in the ethanol preference and in the volun-
tary intake of ethanol solutions over baseline drinking
conditions, when alcohol is reinstated after a period of
abstinence [6]. The negative consequences of withdrawal,
trigger further drinking and has been hypothesized to be
an animal model of alcohol craving [5]. An ADE and the
modification of ethanol intake by exposure to repeated
cycles of alcohol availability and deprivation has been
demonstrated in the selectively bred alcohol-preferring
(P) and high-alcohol-drinking (HAD) line of rats [4,7,8]
but not in Sardinian alcohol preferring (sP) rats [9].
However the effects of repeated deprivations or access to
different ethanol concentrations have not been tested in
the high-alcohol-drinking (UChB) rats, selectively bred
in this laboratory for high volun tary ethano l consumption
using the two-bottle choice (10% v/v ethanol and water)
paradigm [10,11]. The UChB rats slowly increased their
intake of ethanol over 20 days in the free choice condi-
tion to a steady state point reaching 7-9 g ethanol per kg
body weight per day. The gradual increase in the ethanol
consumption displayed by the UChB rats across the time
appeared to be the results of neuroadaptative changes
subsequent to chronic intake. The objective of this study
is to examine whether UChB rats would display an ADE
and a shift in ethanol concentration preference from
lower concentrations (10%) to higher concentration
(20%) of ethanol across deprivation cycles.
2. Animals and Methods
2.1. Animals
The animals were female UChB rats from the 82nd gen-
eration (bred at Schoo l of Medicine, University of Chile).
At three months old, rats were housed individually in
cages where they received concurrent free access to 10%
(v/v) , 20% (v/v) ethanol and water and solid food ad
libitum for 8 weeks Rats were maintained on a 12-hr
reversed light/dark cycle (lights off at 19.00 hr). During
the duration of testing, animals were weighted weekly.
All procedures used in this study were in compliance
with the Chilean Ethical animals rules.
2.2. Experimental Procedure
After the period of 8 weeks under the concurrent free
choice condition between 10%, 20% ethanol and water
paradigm, nine animals were deprived from ethanol for
15 consecutives days (alcohol deprivation period). After
the first deprivation period, rats received a continuous
free-choice access to both ethanol solutions (10%, 20%)
and water for an additional two-week period and ethanol
and water consumption recorded every 24 hours (1st
ADE). After these 2 weeks of ethanol re-exposure, rats
were again deprived of ethanol for 2 additional weeks,
followed by 2 weeks of ethanol exposure (2nd ADE).
This cycle was again repeated (3rd ADE). Results are
expressed as grams of total ethanol intake related to kg-
body weight per day, and as grams of ethanol of each
ethanol solution (10% or 20%) consumed per kg- body
weight per day. Total water intake (water present in
ethanol solution plus water from the water tube) was
expressed as ml/kg/day). Base data were the average of 7
days immediately before deprivation. An additional
group of nine rats was never deprived of ethanol and
served as non deprived controls and their consumption
were evaluated at 8 weeks and at 18 weeks of continuous
ethanol consumption.
2.3. Statistical Analysis
Data is expressed as the mean SEM of each condition.
To determine whether consumption of total ethanol or for
a particular ethanol solution was increased after ethanol
re-exposure, individual repeated measures ANOVA were
performed separately on each of the deprivation groups
and compared to the base data of the non deprived group.
All post hoc comparisons were performed by using the
Neuman-Keuls test. P < 0.05 was considered statistically
significant.
3. Results
Effect of Deprivation on Post-Daily Ethanol In-
take by UChB Rats
After the first deprivation period (1st ADE), UChB rats
displayed a significant increase in the total amount of
ethanol consumed during ethanol re-exposure (Figure 1).
Studies over a period of 24 hours a day showed a sig-
nificant increase in ethanol intake (F(6,69) = 8.55; p <
001). A post hoc analysis revealed that the mean daily
ethanol intake of the rats was significantly higher during
the initial 2 days after re-exposure, compared to base
ethanol intake. Also after the second deprivation period
(2nd ADE) and third deprivation period (3rd ADE) rats
significantly increased their total ethanol consumption
after ethanol re-exposure (F6,69) = 9.74; p < 0.001 and
(F(6,69) = 7.21; p< 0.001 respectively (Figure 1). The
post hoc analysis revealed a significant increase of etha-
nol intake following the first 2 days of re-exposure (Fig-
ure 1). No significant statistical difference in the total
ethanol intake, analyzed by the one way ANOVA
(F(3,165) = 0.3 was observed between 1st, 2nd or 3rd
ADE (Figure 1). Each time ethanol intake returns to the

L. TAMPIER ET AL.
3
baseline around 7 .5 g/kg/day. Total water intake (su m of
water from ethanol solution plus water from the water
tube) about 100 to 120 ml/kg body weight/day, remains
stable during the entire experimental period.
The patterns of the two ethanol solutions, consumed dur-
ing 24 hours of consumption are depicted in Figure 2.
The intake of 20% ethanol increased after the ethanol
re-exposure (F(6, 69) = 3.62; p < 0.005). The post hoc
analysis revealed that the amount of 20% ethanol solu-
tion increased during the initial 2 days of ethanol re-ex-
posure. Whereas, the amount of the 10% ethanol solution
did not show a significant difference (F6,69) = 2.8; n.s.
The preference for the 10% ethanol solution remains
stable. The increase in ethanol consumption after the 2nd
ADE and 3rd ADE was also due to a shift in the prefer-
ence for the more concentrated 20% ethanol solution
(F6,69) = 6.94; p < 0.001 and (F6,69) = 4.64; p <
0.001) respectively. The post hoc analysis revealed that
the intake of the 20% ethanol solution is significantly
higher during the first two days of ethanol re-exposure
(Figure 2). Rats show a preference for the more concen-
trated ethanol solution. Overall there was a significant
increase in ethanol intake and an effect of ethanol con-
centrations.
The total ethanol consumption and the relative intakes
of the 10 and 20% ethanol solutions and water, in the
non deprived UChB rats, under a 24-hr free-choice con-
ditions appears in Table 1 . Each value is the mean of th e
last seven consecutive days of the period of 8-weeks of
*Significantly higher than base data.
Figure 1. The mean (SEM) total amount of ethanol con-
sumed (g/kg/day) by UChB rats under 24-hr free-choice
condition, deprived of ethanol for 2 weeks and then sub-
jected to one to three cycles of 2 weeks of ethanol drinking
and 2 weeks of deprivation (1st, 2nd and 3rd ADE).
*Significantly higher than the base data of the 20% ethanol
solution.
Figure 2. The mean (SEM) of ethanol 10% and 20% con-
sumed (g/kg/day) by UChB rats under 24-hr free-choice
condition, deprived of ethanol for 2 weeks and then sub-
jected to one to three cycles of 2 weeks of ethanol drinking
and 2 weeks of deprivation (1st, 2nd and 3rd ADE)
Table 1. Ethanol, water and total water intake in non de-
prived UChB controls rats at two periods of continuous
access to a 10%, 20% v/v ethanol solution and water.
After 8 weeks 18 weeks
Ethanol intake g/kg/day g/kg/day
Total ethanol 7.35  0.44 7.80  0.5
10% ethanol 6.36  0.42 6.00  0.31
20% ethanol 0.99  0.19 1.36  0.50
Water intake ml/kg/day ml/kg/day
Water 25  5 20  8
Total water intake118.1  6.7 116.6  7.8
ethanol free choice consumption and the last seven con-
secutive days after a period of 18 weeks of continuous
ethanol consumption.
The non deprived group that was allowed to have 24-hr
continuous access to ethanol during all the 18 weeks of
the experiments never approached intakes as seen after

4 L. TAMPIER ET AL.
each deprivation. Also, the base ethanol intake (g/kg/
day), the average of the 7 days immediately before dep-
rivation did not change as a result of the deprivation pe-
riods. Data analyzed by one-way ANOVA indicate no
significant difference in the total ethanol intake (F2,29)
= 0.02; ns; 10% ethanol intake (F2,29)=0.27; ns and
20% ethanol intake (F2,29) = 0.19; ns between base
data.
4. Discussion
UChB rats consuming ethanol voluntarily for two
months, exhibit a robust ADE after a single deprivation
period of two weeks. The increased alcohol intake during
the early days of re-exposure, following a withdrawal
phase, is attributed to a shift in preference towards the
higher concentration of ethanol that might reflect an in-
crease in craving for alcohol, which returns to baseline
after a period of two day s .
Examining the effects of the second or third depriva-
tion on ethanol intake, during the initial 24-hr period
after the reinstatement of ethanol, the second and third
deprivation cycle did not enhance the amount of ethanol
intake above that was attained with the first deprivation.
This could be the result of a ceiling effect (i.e. rats are
drinking as much as possible under the experimental
conditions). Repeated ADE evoked a drinking pattern in
UChB rats very similar to that ob serv ed in P rats [8]. The
increase in the amount of ethanol consumed was not the
result of an indiscriminating polydipsia generated by the
period of abstinence. The total fluid intake by rats (sum
of water from ethanol solution plus water from the water
tube) was not altered during all the period of the study.
The effects observed after a single deprivation or re-
peated deprivations were not observed in the non de-
prived control group, suggesting that chronic exposure to
ethanol alone is not sufficient to produce such a marked
increase in ethanol intake or a shift in preference for
higher concentrations of ethanol.
Uncontrolled alcohol drinking behavior can be as-
sessed after prolonged drug self-administration in some
individuals, and similar to those humans, some rats se-
lectively bred for their high voluntary ethanol consump-
tion can also develop addiction-like behaviours, sug-
gesting that specific genetic factors are involved in the
transition between high ethanol intake and development
of an alcohol deprivation effect [12,13]. Therefore, the
results suggest that neurobiological alterations may be
occurring during time and these alterations result in a
marked increased of ethanol consumption and to the de-
velopment of uncontrolled alcohol-drinking behavior.
Another approach to evaluate the occurrence and the
degree of addiction in laboratory animals are based on
changes in alcohol intake by making drug seeking con-
sistently resistant to interfering factors like concurrent
choice of preferred flavours such as saccharin or sucrose
[14]. This condition can also been ob served in UChB rats.
The placement of a third bottle containing a highly pal-
atable 0.2% saccharin solution, decreased the ethanol
intake in UChB rats that were exposed for a period of 7
days to a 10% ethanol and water under free choice con-
dition, but not in UChB rats exposed to the 10% ethanol
solution for a period of 60 days [15]. Moreover, it is
known that addicts lost the ability to stop drinking and
continue seeking drugs in spite of adverse environmental
conditions. As a matter of fact, it has been previously
observed that under chronic ethanol intake UChB rats
leads to marked tolerance to the aversive effects of disul-
firam and cyanamide on ethanol intake despite the pres-
ence of consistently high levels of blood acetaldehyde
[16]. These results are in accord also to the notion that
UChB rats develop uncontrolled alcohol-drinking be-
haviour, because of its resistance to the aversive effects
produced by an increase in blood acetaldehyde levels.
There are several independent lines of evidence for
genetic contributions to vulnerability to alcoholism [17].
Genetics is just beginning to illuminate the variations
among individuals in their response to alcohol and one
question is what are the changes in the brain that underlie
the transition from contro lled to uncontro lled alcohol use.
According to Nestler [18,19], repeated exposure to a
drug of abuse alters the amounts, and even the types of
genes expressed in specific brain regions resulting in
alterations in molecular and cellular mechanisms that
underlie long-term associative memories in several fore-
brain circuits. Whereas some alcoholics can cease drink-
ing, others cannot. Despite multiple episodes of treat-
ment, and despite risk of significant life problems, re-
lapses to alcohol drinking is very frequent. As a matter of
fact, the alcohol deprivation effect (ADE) has been pro-
posed as an animal model of “loss of control” and “re-
lapse-like” drinking [4,5]. Since an alcohol deprivation
effect (ADE) is also observed in UChB rats make this
line of rats selectively bred for their high voluntary
ethanol consumption, a useful model for study the effi-
cacy of pharmacological agents for the treatment of re-
lapse of ethanol consumption.
5. Conclusions
Relapse to alcohol use after prolonged withdrawal peri-
ods is the major problem in the treatment of alcohol de-
pendence in humans. However, there are relatively few
studies concentrated on elucidation of the neurochemical
events underlying relapse to alcohol. The ADE is a use-
ful model for studying alcohol relapse in both rats and

L. TAMPIER ET AL.
5
mice. Genetics, stress, and environmental cues are all
important factors that influence relapse. Long-term al-
terations in neuronal activity within the glutamatergic
and dopaminergic/serotoninergic systems, appears to
underlie alcohol relapse.
6. Acknowledgements
We thank Mr. Juan Santibáñez for the expert care of the
animals.
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