| Content: | Objectives: Due to the high coexistence of drug abuse in humans who suffer from eating disorders, many studies have suggested that these disorders share a common underlying neurobiological mechanism. A potential candidate that may be involved in both disorders is neuropeptide Y (NPY), an orexigenic neuropeptide considered to be the brain’s most powerful stimulant of feeding. The present study examined the effect of NPY infusions on heroin self-administration and reinstatement of extinguished heroin seeking, an animal model of drug relapse.
Material and Methods: Long Evans male rats were trained to self-administer heroin (0.05 mg/kg/infusion, i.v.) for 1 3-hr session/day for 10 days on a fixed-ratio 1 schedule of reinforcement. Experiment I: Following training, rats received infusions of NPY (0.0, 4.0, and 10.0 µg/rat, i.c.v.) 15 min before the self-administration sessions, in a counter balanced order. Experiment II: In a different group, following heroin self-administration training and extinction of drug seeking by removing the drug from the system, the rats were tested for reinstatement after they received double infusions (one p.m., and one a.m. just before the test session) of NPY (0.0, 4.0, and 10.0 µg/rat i.c.v.).
Results: NPY infusions significantly and dose-dependently increased the rate of heroin infusions. In addition, NPY increased drug-seeking behavior (lever presses) in the absence of drug.
Conclusion: NPY increased on-going heroin self-administration and induced reinstatement of heroin seeking behavior. These results suggest that in addition to its effect on food intake, NPY can modulate the reinforcing and conditioned properties of heroin. |
