Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
319967 | European Neuropsychopharmacology | 2007 | 7 Pages |
The present study evaluated the effects of different histamine receptor agonists and antagonists on the nociceptive response in the mouse formalin test. Intracerebroventricular (20–40 μg/mouse i.c.v.) or subcutaneous (1–10 mg/kg s.c.) injection of HTMT (H1 receptor agonist) elicited a dose-related hyperalgesia in the early and late phases. Conversely, intraperitoneal (20 and 30 mg/kg i.p.) injection of dexchlorpheniramine (H1 receptor antagonist) was antinociceptive in both phases. At a dose ineffective per se, dexchlorpheniramine (10 mg/kg i.p.) antagonized the hyperalgesia induced by HTMT (40 μg/mouse i.c.v. or 10 mg/kg s.c.). Dimaprit (H2 receptor agonist, 30 mg/kg i.p.) and ranitidine (H2 receptor antagonist, 20 and 40 mg/kg i.p.) reduced the nociceptive responses in the early and late phases. No significant change in the antinociceptive activity was found following the combination of dimaprit (30 mg/kg i.p.) with ranitidine (10 mg/kg i.p.). The antinociceptive effect of dimaprit (30 mg/kg i.p.) was prevented by naloxone (5 mg/kg i.p.) in the early phase or by imetit (H3 receptor agonist, 25 mg/kg i.p.) in both early and late phases. The histamine H3 receptor agonist imetit was hyperalgesic following i.p. administration of 50 mg/kg. Imetit-induced hyperalgesia was completely prevented by treatment with a dose ineffective per se of thioperamide (H3 receptor antagonist, 5 mg/kg i.p.). The results suggest that histamine H1 and H3 receptor activations increase sensitivity to nociceptive stimulus in the formalin test.