Chronic exposure to noise modifies the anxiogenic response, but not the hypoactivity, detected on withdrawal from chronic ethanol treatment.

Two groups of rats received chronic ethanol treatment in quiet or noisy housing conditions. Animals from both housing conditions were then withdrawn from ethanol for 12 h prior to testing in the social interaction and elevated plus-maze tests of anxiety. Both ethanol withdrawal groups showed marked hypoactivity (decreased motor activity and decreased closed arm entries in the plus-maze), but they differed in their anxiogenic response (decreased social interaction and percentage of time spent on the open arms), with only the group treated in quiet conditions showing a significant response. A similar pattern of results was found in rats tested 18 h after withdrawal and thus it is unlikely that the anxiogenic response was simply delayed in time. It therefore seemed that chronic exposure to noise during the chronic ethanol treatment modifies dependence, but only as assessed by measures reflecting anxiety. This implies that the adaptive changes are suppressed only in the neural pathways mediating anxiety; possible mediating factors are discussed.