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- Title
Effect of baclofen on cocaine self-administration in rats reinforced under fixed-ratio 1 and progressive-ratio schedules.
- Authors
Brebner, K.; Phelan, R.; Roberts, D. C. S.
- Abstract
Abstract Rationale: Recent reports have indicated that the gamma-aminobutyric acid (GABA)B agonist baclofen attenuates the reinforcing effects of cocaine. Objectives: To further evaluate the effect of baclofcn on cocaine self-administration under a fixed ratio (FR) and progressive ratio (PR) schedule of reinforcement. Methods: In the first series of experiments, three dose-response curves were generated that examined the effect of three doses of baclofen (1.8, 3.2, or 5.6 mg/kg, i.p.) against four unit-injection doses of cocaine (0.19, 0.38, 0.75, and 1.5 mg/kg per injection) reinforced under a FR1 schedule. For comparison, an additional group of rats was pretreated with haloperidol (32, 56, or 100 lag/kg, i.p.). A separate experiment examined the effect of baclofen (1.8, 3.2, or 5.6 mg/kg, i.p.) on responding for concurrently available cocaine or food reinforcement. Results: Under the FR1 schedule, baclofen suppressed intake of low but not high unit injection doses of cocaine. In contrast to haloperidol, baclofen had no effect on the distribution of inter-injection intervals and, instead, produced long pauses in cocaine sell-administration. Baclofen dose dependently reduced cocainereinforced responding on a PR schedule; concurrent access to a food-reinforced lever demonstrated that the animals retained the capacity to respond at high rates. Conclusion: The effect of baclofen pretreatment on cocaine self-administration is dependent on the unit injection dose of cocaine and on the response requirements of the schedule.
- Subjects
AMINOBUTYRIC acid; COCAINE; ANIMAL models in research
- Publication
Psychopharmacology, 2000, Vol 148, Issue 3, p314
- ISSN
0033-3158
- Publication type
Article
- DOI
10.1007/s002130050056