Dopamine receptor subtypes and formalin test analgesia. |
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Authors: | M J Morgan K B Franklin |
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Affiliation: | Department of Psychology, McGill University, Montreal, Quebec, Canada. |
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Abstract: | The role played by dopamine D1 and D2 receptors in formalin test analgesia was explored by challenging D-amphetamine- and morphine-induced analgesia with mixed and selective D1 and D2 antagonists, and by examining the relative analgesic activity of mixed and selective D1 and D2 agonists. The mixed D1/D2 dopamine antagonist cis-flupenthixol (0.5 mg/kg), the D2 antagonist pimozide (0.5 mg/kg), and the D1 antagonist SCH 23390 (0.1 mg/kg) attenuated both D-amphetamine and morphine analgesia. The mixed D1/D2 agonist apomorphine and the selective D2 agonist quinpirole produced dose-dependent analgesia while the selective D1 agonist SKF 38393 was without effect. These data suggest that D1 receptors play an "enabling" role in D2 receptor-mediated analgesia in the formalin test. |
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