Participation of the sympathetic system in acetic acid-induced writhing in mice.
We investigated the participation of a sympathetic component in the abdominal contortions induced by intraperitoneal injection of 0.6% acetic acid in the mouse. The beta blocker propranolol (4 mg/kg, sc) caused a small significant (19%) blockade of the contortions but strongly potentiated (greater than 80%) the effect of indomethacin (30% at 5 mg/kg, sc). Significant inhibition of writhing was also observed with sympatholytics such as guanethidine (27% at 30 mg/kg, sc) and by a specific dopamine-I antagonist, SCH 23390 (62% at 400 micrograms/kg, sc). Tyramine, which releases sympathomimetic amines, and cocaine, which partially blocks the uptake of amines, potentiated acetic acid writhing. Intraperitoneal administration of noradrenaline (187 micrograms/kg)potentiated acetic acid-induced writhing. These results are consistent with the suggestion of Nakamura and Ferreira (1) that inflammatory nociception has a dual component: one mediated by cyclooxygenase metabolites and another by sympathetic amines, possibly acting through a DA-1 type receptor.
Duarte
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ID
Departamento de Farmacologia, Universidade, Federal de Minas Gerais, Belo Horizonte, Brasil.
Nakamura
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M
Ferreira
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SH
D000085:Acetates / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D051379:Mice; D012640:Seizures / Q000139:chemically induced*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013565:Sympatholytics / Q000494:pharmacology
D000085:Acetates; D013565:Sympatholytics; D007213:Indomethacin