Home cage activity and ingestive behaviors in mice following chronic ethanol vapor inhalation

Abstract

Although drug withdrawal may induce an anxiety-like state, decreased locomotion in tests of anxiety-like behavior is an almost universal finding in rodent studies of ethanol withdrawal. Decreased locomotion in many behavioral apparatus, either as a result of a withdrawal-induced lethargy, malaise, or reduced motivation to explore confounds interpreting the effects of withdrawal as specifically increasing an anxiety-like state. To address this issue, we measured home cage activity levels as well as food and water intake for 3 days prior to and up to 5 days after chronic ethanol vapor exposure in genetically heterogeneous mice. In the first experiment, ethanol-withdrawing WSC-2 mice drank less water than controls, but did not differ from controls on any other behavioral measure during the withdrawal assessments. When the dose of ethanol was elevated in a subsequent experiment in WSC-2 mice, a similar temporary decrease in food and water intake, but not in locomotion, was observed during withdrawal. These results differed from those of mice placed into activity monitors during peak withdrawal, which exhibited profoundly reduced activity levels compared to controls. Finally, home cage activity levels during withdrawal were only transiently decreased in a mouse line that has been selectively bred to display high ethanol withdrawal handling-induced convulsion severity (WSP mice). The reduction in food and water consumption seen in most experiments suggests that withdrawal may induce a temporary malaise-like state, but this state is not reflected in altered home cage activity levels. Further, even in a relatively severe mouse model of alcohol withdrawal, any decreases in general home cage activity are short-lived.