title: Interaction of inducible nitric oxide synthase and cyclooxygenase-2 inhibitors in formalin-induced nociception in mice.
abstract: Studies with inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 inhibitor were conducted to assess their synergistic antinociceptive effect and possible therapeutic advantage. The antinociceptive interaction of rofecoxib, a selective cyclooxygenase-2 inhibitor, with aminoguanidine hydrochloride, a selective iNOS inhibitor, was examined in the formalin-induced paw-licking model in mice. Analysis of variance (ANOVA) and the isobolographic method were used to identify the nature of the antinociceptive interaction. Different doses of rofecoxib (1, 3, 10 and 30 mg/kg) and aminoguanidine hydrochloride (10, 30, 100 and 300 mg/kg) alone were administered orally to adult male albino mice (20-30 g). Only high doses of rofecoxib (10 and 30 mg/kg) and aminoguanidine hydrochloride (100 and 300 mg/kg) showed a statistically significant antinociceptive effect. Combination of a subthreshold dose of rofecoxib (1 mg/kg) with increasing doses of aminoguanidine hydrochloride (30, 100 and 300 mg/kg) resulted in potentiated antinociception (P<0.05). Combined therapy with a subthreshold dose of aminoguanidine hydrochloride (30 mg/kg) with increasing doses of rofecoxib (1, 3, 10 and 30 mg/kg) also resulted in significant antinociception (P<0.05). These results suggest that rofecoxib and aminoguanidine hydrochloride act synergistically in their antinociceptive action in mice. A possible mechanism of interaction is that nitric oxide (NO) stimulates the activity of cyclooxygenase-2 by combining with its heme component. Furthermore, the present results suggest that combination therapy with rofecoxib and aminoguanidine hydrochloride may provide an alternative for the clinical control of pain.
authors.affiliation: Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar, Dist., Bareilly Pin-243 122, U.P. India.
authors.forename: Shailesh P
authors.initials: SP
authors.lastname: Dudhgaonkar
authors.forename: Dinesh
authors.initials: D
authors.lastname: Kumar
authors.forename: Ajit
authors.initials: A
authors.lastname: Naik
authors.forename: Aruna R
authors.initials: AR
authors.lastname: Devi
authors.forename: Dnyaneshwar U
authors.initials: DU
authors.lastname: Bawankule
authors.forename: Surendra K
authors.initials: SK
authors.lastname: Tandan
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005557:Formaldehyde; D006146:Guanidines / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D007783:Lactones / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D051379:Mice; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy*; D010147:Pain Measurement; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D013450:Sulfones / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D006146:Guanidines; D007783:Lactones; D013450:Sulfones; C116926:rofecoxib; D005557:Formaldehyde; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C004479:pimagedine