Chinese herbal medicine has been used for thousands of years in China and other Asian countries to treat a variety of inflammatory diseases. The classic Chinese herbal formula,
Huo Luo Xiao Ling Dan (HLXL) is commonly used in traditional Chinese herbal medicine for the treatment of
joint pain and other symptoms of
arthritis. The present study is an investigation of the effects of a modified HLXL extract on persistent
hyperalgesia and
edema in rats with peripheral
inflammation.
Inflammation was induced by injecting complete
Freund's adjuvant (CFA) into one hind paw. Four dosages of the extract were compared to a vehicle control. Each was administered intragastrally (i.g.) daily for seven days beginning one day before CFA.
Hyperalgesia was assessed using a paw withdrawal latency (PWL) test and
edema was determined by measuring paw thickness at pre-CFA and 2 hours, 24 hours, and 5 days post-CFA. Immunohistochemistry was performed 2 hours post-CFA to determine spinal Fos
protein expression. Adverse effects of the extract were monitored by observing the animals closely for unusual behavioral changes. Compared to the control, HLXL at the two lower dosages (0.575 g/kg and 1.15 g/kg) were effective in the later stage (day 5) of inflammatory
hyperalgesia and
edema, while the two higher dosages (2.3 g/kg and 4.6 g/kg) alleviated early stage hind paw
inflammation and
hyperalgesia and facilitated recovery from paw
edema and
hyperalgesia during the late stage. HLXL at 2.30 g/kg significantly suppressed Fos expression in laminae I-II, III-IV and V-VI ipsilaterally and in III-IV contralaterally. No significant signs of toxicity or adverse effects were observed. The data suggest that HLXL dosage-dependently attenuates CFA-induced
inflammation and
hyperalgesia, at least in part by inhibiting noxious transmission at the dorsal horn of the spinal cord.