UC San Diego

Drug addiction is a spiraling and debilitating condition that has severe social and economic consequences for the individual and society. Recently, much work has examined the relationship between drug addiction and the circadian timing system. The master circadian pacemaker directs a daily temporal rhythm throughout the brain and body including the consumption of alcohol. Many drugs, including alcohol, can have myriad effects at different times of day. Conversely, alcohol can alter circadian physiology at multiple levels within the system. Few studies, however, have examined the role that the timing of chronic drug exposure and withdrawal plays in the development and maintenance of drug addiction. Alcohol use, for example, follows a circadian pattern with consumption peaking in the early evening in non-dependent individuals and withdrawal likely occurring late at night. In the transition to dependence, however, craving and consumption expand earlier into the day. What consequences this altered timing of drug use plays in the physiological and psychological consequences of drug addiction remains to be seen. Herein, we specifically examine if: 1) controlling for time of day in alcohol exposure/withdrawal can alter the development of physical dependence, 2) the development of psychological dependence, and 3) if time of day can become a conditioned environmental cue that triggers craving and behavioral sensitization in an amphetamine model of addiction