Some people who use cocaine take it regularly; others binge, sometimes for days, and then stop use for a while. How drug seeking increases during abstinence (called incubation of craving) is of great interest to scientists.
Studying rats exposed to cocaine, researchers at NIDA’s Intramural Research Program (IRP) wanted to determine if the incubation of craving would be different in male and female rats and if the effect is stronger after binge cocaine intake, compared to continuous use. Results have recently been published in the journal Biological Psychiatry.
In this study, male and female rats self-administered cocaine either continuously or intermittently over an 8-hour period. This administration schedule was followed for 12 days. Then, after either 2 or 29 days without access to cocaine, the animals were once again placed in the same environment where they previously self-administered cocaine, and the researchers measured the response for cocaine-associated cues.
The intermittent schedule was designed to model binge use patterns observed in people. In both males and females, cocaine seeking was higher after intermittent drug access than continuous access, suggesting that binge use might prompt stronger cravings. Interestingly, cocaine seeking was higher in female rats than in male rats in both models. In fact, in female rats, incubation of craving after either intermittent or continuous drug access was significantly higher during estrus, the active period in their reproductive cycle. The scientists note that a question for future research would be to examine if cocaine craving in female humans is modulated by the menstrual cycle.
Study:
- Nicolas, Celine; Russell, Trinity I; Pierce, Anne F; Maldera, Steeve; Holley, Amanda; You, Zhi-Bing; McCarthy, Margaret M; Shaham, Yavin; Ikemoto, Satoshi. Incubation of Cocaine Craving After Intermittent-Access Self-administration: Sex Differences and Estrous Cycle. Biological Psychiatry.