Masakazu Yoshimura1, Norifumi Yonehara2, Takashi
Ito3, Yoichiro Kawai1 and Takashi Tamura1
1CentralﾊResearch Laboratories, Maruishi Pharmaceutical Co.,
Ltd., 2-2-18 Imazu-Naka, Tsurumi-ku, Osaka 538-0042, Japan
2Departmentﾊof Pharmacology and 3Department of Oral
& Maxillofacial Surgery 2,
Osaka University Faculty of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871,
Japan
Abstract: The effects of capsaicin cream on neurogenic inflammation
and thermal nociceptive threshold were investigated in rats. Firstly, for
topical application of capsaicin cream to hind paw, we shaped boots from
dental cement to prevent the animals from licking off the drug. Capsaicin
cream (1%) led to significant increases in the amounts of Evans blue and
substanceﾊP (SP) released into the perfusate, and the former response was
significantly suppressed by pretreatment with RP67580, an NK1-receptor
antagonist, but not by treatment with an NK2-receptor antagonist.
Subsequent electrical stimulation of the sciatic nerve resulted in a significant
reduction in Evans blue and SP extravasation 24ﾊh after topical application
of capsaicin cream. On the other hand, when capsaicin cream was repeatedly
applied to both hind paws once a day, withdrawal latency for noxious heat
stimulation decreased after 24ﾊh, and this thermal hyperalgesia was reversed
3ﾊdays later. These results suggest that capsaicin cream initially affects
neurogenic inflammation mechanisms and then blocks the pain transmission
mechanism.
Keywords: Capsaicin cream, Analgesic, Neurogenic inflammation, Substance
p