Effects of selective D1 and D2 dopamine antagonists on cocaine self-administration in the rat
The effect of the selective D1 antagonist, SCH 23390, and the selective D2 antagonist, spiperone, was investigated in rats trained to self-administer intravenous cocaine on a fixed-ratio (FR) 5 schedule of reinforcement. Both SCH 23390 and spiperone pretreatment increased responding up to doses of 10.0 µg/kg, and decreased responding at higher doses. Since rate of responding maintained by a drug can be influenced by factors other than its reinforcing efficacy, behavior maintained by cocaine was also investigated under a progressive-ratio schedule. The breaking point obtained under this schedule is used as a measure of the efficacy of the reinforcer and this value is not exclusively determined by response rate. With the progressive-ratio schedule, both SCH 23390 and spiperone produced dose-dependent decreases in the highest ratio completed in rats self-administering cocaine. The results obtained using the FR 5 and progressive-ratio schedules suggest that both D1 and D2 receptors are involved in mediating the reinforcing effects of cocaine.
Key wordsSCH 23390 Spiperone Cocaine Self-administration Dopamine Fixed-ratio schedule Progressive-ratio schedule
Unable to display preview. Download preview PDF.
- Koob GF, Vaccarino F, Amalric M, Bloom FE (1987b) Positive reinforcement properties of drugs: search for neural substrates. In: Engel J, Oreland L (eds) Brain reward systems and abuse. Raven Press, New York, pp 35–50Google Scholar
- Weeks JR (1972) Long-term intravenous infusion. In: Myers RD (ed) Methods in psychobiology, vol 2. Academic Press, London, pp 155–168Google Scholar