1. Per2MUTATION INCREASES DURATION AND FREQUENCY OF ETHANOL DRINKING AND ENHANCES COCAINE CLOCK-RESETTING RESPONSES Allison J. Brager, Adam C. Stowie, Rebecca A. Prosser, and J. David Glass COCAINE Does Per2mutation affect response to different drugs of abuse? ETHANOL YES. The Per2clock gene mutation increases the seeking of, and sensitivity to, various classes of abused drugs.