Increased impulsivity after injected alcohol predicts later alcohol consumption in rats: evidence for "loss-of-control drinking" and marked individual differences.

A delay-of-reward paradigm was used to assess impulsivity in rats. Previous research with this paradigm has found that normally occurring impulsivity scores predict magnitude of voluntary alcohol intake. The authors' primary findings were (a) injected alcohol produced a dose-dependent increase in impulsivity, (b) varying the intervals between alcohol and testing yielded orderly effects, (c) there were extreme individual differences in impulsive reactivity to alcohol, (d) these individual differences did not reflect differences in alcohol pharmacokinetics, (e) subject selection procedures ensured that differences in impulsive reactivity to alcohol were independent of significant variations in baseline impulsivity scores, and (f) individual differences in impulsive reactivity to injected alcohol strongly predicted magnitude of voluntary alcohol intake. The findings are discussed in terms of evidence for a dysfunctional alcohol-induced positive feedback loop ("loss-of-control drinking"), alcohol disinhibition, and the relationship between impulse control and the regulation of alcohol consumption.