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Abstract
Clinical evidence often points to stress as a cause or an antecedent to the development
of drinking problems. Yet, animal models of alcohol drinking have yielded inconsistent
evidence for a direct contribution of stress, and many studies have shown that stress
suppresses alcohol consumption. The aim of the present study was to examine alcohol
reward in animals exposed to repeated, mild social stress, and to determine whether
alcohol drinking changes as a function of the temporal parameters of alcohol access
relative to the stressor. Male Long-Evans rats, trained to self-administer a 6% (wt/vol)
alcohol solution using a sucrose-fading procedure, were exposed to five brief (5min)
episodes of contact with an aggressive male. Full contact with the resident was limited
to a single episode of defeat, whereas the following four encounters occurred with
the subjects behind a protective wire mesh cage. Alcohol self-administration was measured
1 week prior to stress (baseline), on each day of stress exposure, and 1 week following
stress. Separate groups of animals were randomly assigned to self-administer alcohol
immediately prior, immediately following, or 2h following defeat stress. Stress preferentially
increased alcohol drinking on stress-exposure days, and further elevated the amount
consumed 1 week following stress. Temporal parameters of alcohol access relative to
the stressor were found to be important. Average alcohol consumption was greatest
for animals drinking 2h postdefeat, whereas animals drinking immediately prior to
or following the stressor did not show a significant increase in alcohol consumption.
Results suggest that mild social defeat stress is sufficient to elicit increases in
alcohol consumption in nonpreferring strains of rodents, provided alcohol access occurs
at an optimal time interval after the social defeat experience.