Citation

Mandt BH, Copenhagen LI, Zahniser NR, Allen RM. Drug Alcohol Depend. 2015; 149: 166-172.

Affiliation

Department of Psychology, University of Colorado Denver, Denver, CO 80217, United States.

Copyright

(Copyright © 2015, Elsevier Publishing)

DOI

10.1016/j.drugalcdep.2015.01.039

PMID

25697912

Abstract

BACKGROUND: Escalation of consumption is a hallmark of cocaine addiction. Many animal models reveal escalation by increasing the duration of drug access (e.g., 6-24h/day) after longer histories of self-administration. We recently developed a method that reveals escalation early post-acquisition under shorter access conditions. However, whether or not rats will escalate cocaine consumption both early post-acquisition under short access (2h/day) conditions, and later under long access (6h/day) conditions, has not been demonstrated.

METHODS: All rats acquired cocaine self-administration (0.8mg/kg, i.v.) under 2h conditions, and then continued 2h self-administration for an additional 13 sessions. Then, rats were assigned either to 2 or 6h conditions, and self-administered cocaine (0.8mg/kg, i.v.) for an additional 19 sessions. In addition, four cocaine-induced locomotor activity measurements were taken for each rat: before cocaine exposure, after non-contingent cocaine administration, and after escalation in the short and long access experimental phases.

RESULTS: Following acquisition, rats displayed a robust escalation of intake during 2h sessions. Rats that self-administered cocaine in continued 2h sessions exhibited stable intake, whereas rats that self-administered cocaine in 6h sessions further escalated intake. Despite the second escalation in 6h rats, cocaine-induced locomotor activity did not differ between 2 and 6h rats.

CONCLUSIONS: Escalation of cocaine self-administration can occur in the same rats both early post-acquisition, and later under long access conditions. Importantly, this early post-acquisition period provides a new opportunity to determine the mechanisms first involved in the escalation phenomenon.

Language: en