Comparison of self-administration behavior and responsiveness to drug-paired cues in rats running an alley for intravenous heroin and cocaine
✍ Scribed by Zu-In Su; Jennifer Wenzel; Rebeccah Baird; Aaron Ettenberg
- Publisher
- Springer
- Year
- 2010
- Tongue
- English
- Weight
- 290 KB
- Volume
- 214
- Category
- Article
- ISSN
- 0033-3158
No coin nor oath required. For personal study only.
✦ Synopsis
Rationale
Evidence suggests that responsiveness to a drug-paired cue is predicted by the reinforcing magnitude of the drug during prior self-administration. It remains unclear, however, if this principle holds true when comparisons are made across drug reinforcers.
Objective
The current study was therefore devised to test the hypothesis that differences in the animals’ responsiveness to a cocaine- or heroin-paired cue presented during extinction would reflect differences in the patterns of prior cocaine and heroin runway self-administration.
Methods
Rats ran a straight alley for single intravenous injections of either heroin (0.1 mg/kg/inj) or cocaine (1.0 mg/kg/inj) each paired with a distinct olfactory cue. Animals experienced 15 trials with each drug reinforcer in a counterbalanced manner. Start latencies, run times, and retreat behaviors (a form of approach-avoidance conflict) provided behavioral indices of the subjects’ motivation to seek the reinforcer on each trial. Responsiveness to each drug-paired cue was assessed after 7, 14, or 21 days of non-reinforced extinction trials. Other animals underwent conditioned place preference (CPP) testing to ensure that the two drug reinforcers were capable of producing drug–cue associations.
Results
While both drugs produced comparable CPPs, heroin served as a stronger incentive stimulus in the runway as evidenced by faster start and run times and fewer retreats. In contrast, cocaine- but not heroin-paired cues produced increases in drug-seeking behavior during subsequent extinction trials.
Conclusions
The subjects’ responsiveness to drug-paired cues during extinction was not predicted by differences in the motivation to seek heroin versus cocaine during prior drug self-administration.