Abstract
Cocaine addiction has been characterized by a shift from controlled to uncontrolled and compulsive drug use. Using novel self-administration procedures, we attempted to model this transitional phase and characterize the behavioral changes that underlie it. We chose to use food-reinforced responding across the light/dark cycle as an indicator of the degree to which cocaine was disrupting ongoing behavior as a potential measure of dysregulation. Four groups of rats (n=5–6) were given 24-h access to cocaine (1.5 mg/kg/inj) available in 2, 3, 4, or 5 discrete trials/h. All rats were given continuous access to a second lever that resulted in the delivery of a 45 mg food pellet under a fixed ratio 1 schedule. The results showed that under low access conditions (eg 2 discrete trials/h), both food- and cocaine-reinforced responding were diurnally regulated and occurred coincidentally. As access to cocaine was increased, there was a progressive disruption in the diurnal control over both food- and cocaine-maintained responding. High access conditions also produced transient decreases in the total levels of food-reinforced responding. These findings suggest that high access to cocaine under the discrete trial cocaine self-administration procedure produces a transient disruption in the diurnal control over behavior maintained by food and that the level of control (or loss of) may be a useful marker of dysregulation.
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Acknowledgements
We are grateful to April Engram for her technical assistance and to Dr Theresa Lee for her critical comments on a previous version of this manuscript. We would like to acknowledge the Yale Interdisciplinary Women's Health Research Scholar Program on Women and Drug Abuse, NIH Office of Research on Women's Health. This work was supported by NIDA Grants RO1DA14030 and P50DA06634 (DCSR) and T32DA07246 (WJL).
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Lynch, W., Roberts, D. Effects of Cocaine Self-Administration on Food-Reinforced Responding Using a Discrete Trial Procedure in Rats. Neuropsychopharmacol 29, 669–675 (2004). https://doi.org/10.1038/sj.npp.1300363
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DOI: https://doi.org/10.1038/sj.npp.1300363
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