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Assessment of ropinirole as a reinforcer in rhesus monkeys
Kevin B Freeman1, David J Heal, Andrew C McCreary
1Division of Neurobiology and Behavior Research, Department of Psychiatry and Human Behavior, The University of Mississippi Medical Center, Jackson, MS 39216, USA. kfreeman@umc.edu
Background:
Ropinirole, a D(2)/D(3)/5-HT(1A) agonist, is used for the treatment of Parkinson's disease and restless leg syndrome, and is currently being evaluated as a treatment for cocaine dependence. However, there is little information available on ropinirole's reinforcing effects.
Methods:
The current study tested ropinirole in monkeys (n=7) trained to self administer cocaine on a fixed-ratio 25 (FR 25) schedule of reinforcement to determine if it would function as a reinforcer. In addition, a behavioral economics approach was used in four monkeys to compare the reinforcing effectiveness of ropinirole to cocaine.
Results:
Cocaine (0.01-0.3 mg/kg/injection) functioned as a reinforcer in all monkeys under the FR 25 schedule, and ropinirole (0.01-0.1mg/kg/injection) functioned as a reinforcer in all but one. Furthermore, cocaine was a more effective reinforcer than ropinirole as indexed by demand functions.
Conclusion:
The current data indicate that ropinirole has reinforcing effects in monkeys, although its effectiveness as a reinforcer is relatively weak.
