Effects of dopaminergic agents on visceral pain measured by the mouse writhing test

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Frussa-Filho, Roberto [UNIFESP]
Rocha, JBT
Conceição, Isaltino Marcelo da [UNIFESP]
Mello, C. F.
Pereira, M. E.
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The present study explored the role of the dopaminergic transmission in the mouse writhing test analgesia by examining the relative analgesic activity of indirect dopaminergic agonists (amphetamine and cocaine), a mixed D-1/D-2 direct agonist (apomorphine), and a direct D-1 (SKF38393) and D-2 (bromocriptine) dopaminergic agonist.Amphetamine (1, 3 and 10 mg/kg, s,c.), cocaine (3 and 10 mg/kg, s.c.), apomorphine (0.3, 1 and 3 mg/kg, s.c.) and bromocriptine (30 mg/kg, s.c.) induced a significant decrease of the number of writhes, SKF38393 (1, 3, 10 and 30 mg/kg, s,c.) had no effect on writhing.The antinociceptive effect of amphetamine and cocaine was not reversed by naltrexone, haloperidol or SCH23390. The apomorphine- and bromocriptine-induced analgesia was not reduced by naltrexone or SCH23390 but was attenuated by haloperidol: the apomorphine-induced analgesia was not modified by domperidone.The present results suggest an involvement of the dopaminergic transmission in visceral nociception. This dopaminergic component appears to involve exclusively the central D-2 receptor system, and does not seem to be influenced by opioid mechanisms.
Archives Internationales De Pharmacodynamie Et De Therapie. Ghent: Arch Int Pharmacodynamie, v. 331, n. 1, p. 74-93, 1996.