Antidepressant-like effect of ethanol revealed in the forced swimming testin Sardinian alcohol-preferring rats

Rationale: A large body of evidence indicates high comorbidity between depr ession and alcohol abuse. The self-medication hypothesis proposes that depr essed subjects may abuse ethanol because it reduces the symptoms of depress ion. The present study evaluated whether ethanol may exert an antidepressan t-like action in genetically selected alcohol-preferring rats, either Sardi nian alcohol-preferring (sP) or Marchigian Sardinian alcohol-preferring (ms P) rats, and for comparison in Sardinian alcohol-non-preferring (sNP) rats. Methods: The forced swimming test (FST) was used to evaluate the antidepre ssant-like action of ethanol; in this test the effect of ethanol ingestion on the immobility time was determined. Results: Ethanol-naive sP rats exhib ited a longer period of immobility in comparison to sNP rats. Both in ethan ol-naive sP and msP rats, voluntary ethanol drinking reduced the immobility time. A similar effect was obtained when repeated (five or nine) intragast ric administrations of 0.7 g/kg ethanol were given during the 24 h prior to the test in msP and in sP, but not in sNP rats. Desipramine, like ethanol, sharply reduced immobility at doses of 5 or 20 mg/kg, given 3 times in the 24 h before the test in msP rats. The reduced immobility induced by ethano l in msP rats was apparently not the consequence of a general motor activat ion, because 9 IG administrations of ethanol, 0.7 g/kg, failed to alter loc omotor activity in the open field test. Moreover, blood alcohol levels and rectal temperature of msP, sP and sNP after IG ethanol administration were not statistically different. Conclusions: The present results provide evide nce for an antidepressant-like action of ethanol in sP and msP rats and sug gest that this action may contribute to sustain their high ethanol drinking .