We tested
baicalin for its antiinflammatory and
analgesic effects (and the mechanisms) in a rat model of
carrageenan-evoked
thermal hyperalgesia. Pre- or posttreatment with
baicalin (10, 30, or 100 mg/kg intraperitoneally) caused a significant
analgesic effect with a similar effect of dose-matched
ibuprofen. Furthermore,
baicalin dose-dependently attenuated
tumor necrosis factor-alpha (from 3510 +/- 150 pg/mL to 2860 +/- 148 pg/mL to 1480 +/- 210 pg/mL),
interleukin (IL)-1beta (from 3210 +/- 210 pg/mL to 2200 +/- 140 pg/mL to 750 +/- 95 pg/mL), and
IL-6 (from 58.5 +/- 9.8 pg/mL to 38.5 +/- 9.0 to 21.0 +/- 8.1 ng/mL) formation but enhanced
IL-10 (from 18.1 +/- 2.5 pg/mL to 36.1 +/- 5.5 pg/mL to 71.2 +/- 9.5 pg/mL) production in paw exudates at 4 h after
carrageenan injection.
Prostaglandin E(2) (
PGE(2)) and
nitrate formation in the
carrageenan-injected paws were dose-dependently inhibited by
baicalin (10-100 mg/kg intraperitoneally) (
PGE(2): from 15.9 +/- 2.1 ng/mL to 12.1 +/- 1.6 ng/mL to 6.2 +/- 1.8 ng/mL;
nitrate: from 39.8 +/- 4.8 microM to 27.5 +/- 3.0 microM to 17.2 +/- 1.6 microM) at 4 h but not at 1.5 h after
carrageenan injection. Increased
myeloperoxidase activity in
carrageenan-injected paws was also dose-dependently reduced by
baicalin. These findings suggest that the antiinflammatory and
analgesic mechanisms of
baicalin may be associated with the inhibition of critical inflammatory mediators, including
nitric oxide,
PGE(2), and proinflammatory
cytokines, accompanied by an increase in
IL-10 production, as well as neutrophil infiltration at sites of
inflammation.
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