Aqueous extract of Asiasari radix inhibits formalin-induced hyperalgesia via NMDA receptors.
BACKGROUND
Asiasari radix is prepared from Asiasarum sieboldii F. Maekawa or Asiasarum heterotropoides F. Maekawa var. mandshuricum F. Maekawa, widely used for treatment of various tussive, inflammatory, allergic diseases and pain.


OBJECTIVE
The antinociceptive effects of Asiasari radix extract (ARE) in mice were examined.


METHODS
Tail-flick, tail-pressure, hot-plate and formalin tests were used to evaluate its antinociceptive activity. Moreover, N-methyl-D-aspartic acid (NMDA)-induced nociceptive response was also examined.


RESULTS
Oral administration of ARE did not affect the responses of the tail-flick, tail-pressure, or hot-plate test or the first phase of the formalin tests, but it dose-dependently decreased the duration of nociceptive behavior in the second phase, as did diclofenac, a non-steroidal anti-inflammatory drug. ARE also inhibited nociceptive behaviors induced by the intrathecal injection of NMDA, although diclofenac did not affect these behaviors. Pretreatment with bicuculline, a GABA(A) antagonist, reduced the antinociceptive effects of ARE on the formalin- or NMDA-induced behaviors. Muscimol, a GABA(A) agonist, exhibited antinociceptive effects in the formalin test and NMDA-induced behaviors in a manner similar to that of ARE. On the other hand, diclofenac significantly inhibited cyclooxygenase (COX)-1 and -2 activities, while ARE did not.


CONCLUSIONS
These results suggest that ARE may inhibit development of hyperalgesia via NMDA receptors based on activation of GABA(A) receptors in the spinal cord.
Tsumura Research Laboratory, Tsumura & Co., 3586 Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki 300-1192, Japan. suzuki_yasuyuki@mail.tsumura.co.jp
Yasuyuki
Y
Suzuki
Mitsutoshi
M
Yuzurihara
Tomoko
T
Hibino
Shingo
S
Yano
Yoshio
Y
Kase
D000818:Animals; D029065:Aristolochiaceae / Q000737:chemistry*; D005557:Formaldehyde / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006930:Hyperalgesia / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D051379:Mice; D010936:Plant Extracts / Q000494:pharmacology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*
D010936:Plant Extracts; D016194:Receptors, N-Methyl-D-Aspartate; D005557:Formaldehyde