Antinociceptive activity of a synthetic curcuminoid analogue, 2,6-bis-(4-hydroxy-3-methoxybenzylidene)cyclohexanone, on nociception-induced models in mice.

This study investigated the potential antinociceptive efficacy of a novel synthetic curcuminoid analogue, 2,6-bis-(4-hydroxy-3-methoxybenzylidene)cyclohexanone (BHMC), using chemical- and thermal-induced nociception test models in mice. BHMC (0.03, 0.1, 0.3 and 1.0 mg/kg) administered via intraperitoneal route (i.p.) produced significant dose-related inhibition in the acetic acid-induced abdominal constriction test in mice with an ID(50) of 0.15 (0.13-0.18) mg/kg. It was also demonstrated that BHMC produced significant inhibition in both neurogenic (first phase) and inflammatory phases (second phase) of the formalin-induced paw licking test with an ID(50) of 0.35 (0.27-0.46) mg/kg and 0.07 (0.06-0.08) mg/kg, respectively. Similarly, BHMC also exerted significant increase in the response latency period in the hot-plate test. Moreover, the antinociceptive effect of the BHMC in the formalin-induced paw licking test and the hot-plate test was antagonized by pre-treatment with the non-selective opioid receptor antagonist, naloxone. Together, these results indicate that the compound acts both centrally and peripherally. In addition, administration of BHMC exhibited significant inhibition of the neurogenic nociception induced by intraplantar injections of glutamate and capsaicin with ID(50) of 0.66 (0.41-1.07) mg/kg and 0.42 (0.38-0.51) mg/kg, respectively. Finally, it was also shown that BHMC-induced antinociception was devoid of toxic effects and its antinociceptive effect was associated with neither muscle relaxant nor sedative action. In conclusion, BHMC at all doses investigated did not cause any toxic and sedative effects and produced pronounced central and peripheral antinociceptive activities. The central antinociceptive activity of BHMC was possibly mediated through activation of the opioid system as well as inhibition of the glutamatergic system and TRPV1 receptors, while the peripheral antinociceptive activity was perhaps mediated through inhibition of various inflammatory mediators.

Antinociceptive effect of the essential oil of Zingiber zerumbet in mice: possible mechanisms.

ETHNOPHARMACOLOGICAL RELEVANCE: Zingiber zerumbet (L.) Smith, a wild edible ginger species or locally known as "lempoyang", commonly used in the Malays traditional medicine as an appetizer or to treat stomachache, toothache, muscle sprain and as a cure for swelling sores and cuts. AIM: The present study was conducted to investigate the possible mechanism of actions underlying the systemic antinociception activity of the essential oil of Zingiber zerumbet (EOZZ) in chemical-induced nociception tests in mice. MATERIALS AND METHODS: Acetic acid-induced abdominal constriction, capsaicin-, glutamate- and phorbol 12-myristate 13-acetate-induced paw licking tests in mice were employed in the study. In all experiments, EOZZ was administered systemically at the doses of 50, 100, 200 and 300 mg/kg. RESULTS: It was shown that EOZZ given to mice via intraperitoneal and oral routes at 50, 100, 200 and 300 mg/kg produced significant dose dependent antinociception when assessed using acetic acid-induced abdominal writing test with calculated mean ID(50) values of 88.84 mg/kg (80.88-97.57 mg/kg) and 118.8 mg/kg (102.5-137.8 mg/kg), respectively. Likewise, intraperitoneal administration of EOZZ at similar doses produced significant dose dependent inhibition of neurogenic pain induced by intraplantar injection of capsaicin (1.6 µg/paw), glutamate (10 µmol/paw) and phorbol 12-myristate 13-acetate (1.6µg/paw) with calculated mean ID(50) of 128.8 mg/kg (118.6-139.9 mg/kg), 124.8 mg/kg (111.4-139.7 mg/kg) and 40.29 (35.39-45.86) mg/kg, respectively. It was also demonstrated that pretreatment with l-arginine (100mg/kg, i.p.), a nitric oxide precursor significantly reversed antinociception produced by EOZZ suggesting the involvement of l-arginine/nitric oxide pathway. In addition, methylene blue (20mg/kg, i.p.) significantly enhanced antinociception produced by EOZZ. Administration of glibenclamide (10mg/kg, i.p.), an ATP-sensitive K(+) channel antagonist significantly reversed antinociceptive activity induced by EOZZ. CONCLUSION: Together, the present results suggested that EOZZ-induced antinociceptive activity was possibly related to its ability to inhibit glutamatergic system, TRPV1 receptors as well as through activation of l-arginine/nitric oxide/cGMP/protein kinase C/ATP-sensitive K(+) channel pathway.

Possible participation of nitric oxide/cyclic guanosine monophosphate/protein kinase C/ATP-sensitive K(+) channels pathway in the systemic antinociception of flavokawin B.

The possible mechanisms of action in the antinociceptive activity induced by systemic administration (intraperitoneal, i.p.) of flavokawin B (FKB) were analysed using chemical models of nociception in mice. It was demonstrated that i.p. administration of FKB to the mice at 0.3, 1.0, 3.0 and 10 mg/kg produced significant dose-related reduction in the number of abdominal constrictions. The antinociception induced by FKB in the acetic acid test was significantly attenuated by i.p. pre-treatment of mice with L-arginine, the substrate for nitric oxide synthase or glibenclamide, the ATP-sensitive K(+) channel inhibitor, but was enhanced by methylene blue, the non-specific guanylyl cyclase inhibitor. FKB also produced dose-dependent inhibition of licking response caused by intraplantar injection of phorbol 12-myristate 13-acetate, a protein kinase C activator (PKC). Together, these data indicate that the NO/cyclic guanosine monophosphate/PKC/ATP-sensitive K(+) channel pathway possibly participated in the antinociceptive action induced by FKB.

Antinociceptive activity of methanolic extract of Acmella uliginosa (Sw.) Cass.

ETHNOPHARMACOLOGICAL RELEVANCE: Acmella uliginosa (Sw.) Cass. is a medicinal herbaceous plant that is commonly used by the Malay community in Malaysia to relieve pain often associated with mouth ulcers, toothache, sore throat, and stomach ache. AIM: The study was carried out to investigate the antinociceptive effect of the methanolic extract of A. uliginosa (Sw.) Cass. flowers (MEAU) using murine models of chemicals and thermal nociception. MATERIALS AND METHODS: Chemicals (acetic acid-induced abdominal constriction and formalin-, capsaicin-, glutamate-induced paw licking test) and thermal models (hot plate test) of nociception in mice were employed to evaluate the MEAU analgesic effect. The extract was given via oral administration at doses of 3, 10, 30 and 100 mg/kg. RESULTS: It was demonstrated that MEAU produced significant antinociceptive response in all the chemical- and thermal-induced nociception models, which indicates the presence of both centrally and peripherally mediated activities. Furthermore, the reversal of antinociception of MEAU by naloxone suggests the involvement of opioid system in its centrally mediated analgesic activity. Moreover, MEAU-treated mice did not show any significant motor performance alterations. No mortality and signs of toxicity were recorded following treatment of the MEAU. CONCLUSION: The results from the present study appear to support the folkloric belief in the medicinal properties of A. uliginosa (Sw.) Cass. which against pain at both central and peripheral levels, in which the central antinociception is probably due to the participation of the opioid receptors.