Baclofen suppresses motivation to consume alcohol in rats

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Abstract
Recent studies demonstrated that treatment with the γ-aminobutyric acid (GABA)B receptor agonist baclofen reduced alcohol intake in selectively bred Sardinian alcohol-preferring (sP) rats tested under the home-cage, two-bottle choice regimen. The present study investigated the effect of baclofen on the appetitive, rather than consummatory, aspects of alcohol ingestion in sP rats. Rats were trained to lever-press for oral alcohol (10%, v/v) or sucrose (3%, w/v) under a fixed-ratio schedule of 4. Once self-administration behavior was established, alcohol intake averaged approximately 0.7 g/kg over the 30-min session. Subsequently, the effect of the acute administration of baclofen (0, 1, 2 and 3 mg/kg, i.p.) on the extinction responding for alcohol and sucrose (defined as the maximal number of lever responses reached in the absence of reinforcement and used as index of motivation to consume alcohol and sucrose) was evaluated. All doses of baclofen produced a marked suppression of extinction responding for alcohol. Conversely, only the 3-mg/kg baclofen dose significantly affected extinction responding for sucrose. A separate open-field test indicated that baclofen (0, 1, 2 and 3 mg/kg, i.p.) did not affect spontaneous motor activity in sP rats. These results suggest that baclofen may specifically reduce the motivational properties of alcohol; further, these results are in agreement with the recently reported anti-craving potential of baclofen in alcoholics.