| Abstract No.: | B-G2193 |
| Country: | Canada |
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| Title: | ROLE OF µ-OPIOID RECEPTORS IN THE VENTRAL TEGMENTAL AREA IN REACQUISITION OF HEROIN SEEKING IN RATS |
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| Authors/Affiliations: | 1 Martin Sticht*; 1 Francesco Leri;
1 University of Guelph, ON, Canada.
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| Content: | Drug relapse can be conceptualized as a reacquisition process whereby renewed drug use after a period of abstinence causes the re-emergence of drug seeking which, in turn, promotes further drug use eventually resulting in renewed pathological drug intake. In these studies, we employed the conditioned place preference procedure and male Sprague-Dawley rats to investigate the role of µ-opioid receptors in the reacquisition of heroin seeking. Two sets of studies were conducted using a common procedure involving heroin place conditioning (0.3 or 1 mg/kg SC x 4 sessions) followed by a test 24h later, extinction (saline x 4 sessions) followed by a second test 24h later, and heroin reconditioning (0 or 1.0 mg/kg x 1 session) followed by a final test for place preference 24h later. Systemic injections or intra-ventral tegmental area (VTA) infusions of µ-opioid antagonists were administered following the heroin reconditioning session. In the first set of studies it was found that post-reconditioning administration of naloxone (0, 1 or 3 mg/kg) dose-dependently blocked, attenuated and had no effect on reacquisition of heroin seeking when administered 10 min, 1 hour and 6 hours after reconditioning, respectively. In the second set of studies, it was found that post-reconditioning infusions of naloxone methiodide (2 nmol in 0.5 µl) in the VTA, but not in adjacent structures, blocked reacquisition of heroin seeking when administered 10 min, but not 6 hours, after reconditioning. These data indicate that reacquisition of heroin seeking is dependent on the activation of µ-opioid receptors in the VTA, and suggest that these receptors may be critically involved in a putative memory consolidation process that underlies drug relapse.
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