Effects of alcohol on the acquisition and expression of fear-potentiated startle in mouse lines selectively bred for high and low alcohol preference

Abstract

Rationale: Anxiety disorders and alcohol use disorders frequently co-occur in humans perhaps because alcohol relieves anxiety. Studies in humans and rats indicate that alcohol may have greater anxiolytic effects in organisms with increased genetic propensity for high alcohol consumption.

Objectives and methods: The purpose of this study was to investigate the effects of moderate doses of alcohol (0.5, 1.0, 1.5 g/kg) on the acquisition and expression of anxiety-related behavior using a fear-potentiated startle (FPS) procedure. Experiments were conducted in two replicate pairs of mouse lines selectively bred for high- (HAP1 and HAP2) and low- (LAP1 and LAP2) alcohol preference; these lines have previously shown a genetic correlation between alcohol preference and FPS (HAP > LAP; Barrenha and Chester, Alcohol Clin Exp Res 31:1081-1088, 2007). In a control experiment, the effect of diazepam (4.0 mg/kg) on the expression of FPS was tested in HAP2 and LAP2 mice.

Results: The 1.5 g/kg alcohol dose moderately decreased the expression of FPS in both HAP lines but not LAP lines. Alcohol had no effect on the acquisition of FPS in any line. Diazepam reduced FPS to a similar extent in both HAP2 and LAP2 mice.

Conclusions: HAP mice may be more sensitive to the anxiolytic effects of alcohol than LAP mice when alcohol is given prior to the expression of FPS. These data collected in two pairs of HAP/LAP mouse lines suggest that the anxiolytic response to alcohol in HAP mice may be genetically correlated with their propensity toward high alcohol preference and robust FPS.

Fig. 1

Mean (± SEM) % FPS in fear-conditioned (top panels) and control (bottom panels) HAP (left panels) and LAP (right panels) mouse lines treated with IP injections of alcohol (0.5, 1.0, and 1.5 g/kg) or saline before the FPS test session.*p< 0.05 saline vs. 1.5 g/kg group

Fig. 2

Mean (± SEM) % FPS in HAP2 (left panel) and LAP2 (right panel) mouse lines treated with IP injections of 4.0 mg/kg diazepam or vehicle before the FPS test session. *p<0.01 HAP2 vs. LAP2; +p<0.01, vehicle vs. diazepam groups