Hop extract produces antinociception by acting on opioid system in mice.
In the present study, the antinociceptive profiles of hop extract were characterized in ICR mice. Hop extract administered orally (from 25 to 100 mg/kg) showed an antinociceptive effect in a dose-dependent manner as measured in the acetic acid-induced writhing test. Antinociceptive action of hop extract was maintained at least for 60 min. Moreover, cumulative response time of nociceptive behaviors induced with intraplantar formalin injection was reduced by hop extract treatment during the 2nd phases. Furthermore, the cumulative nociceptive response time for intrathecal injection of substance P (0.7 µg) or glutamate (20 µg) was diminished by hop extract. Intraperitoneal pretreatment with naloxone (an opioid receptor antagonist) attenuated antinociceptive effect induced by hop extract in the writhing test. However, methysergide (a 5-HT serotonergic receptor antagonist) or yohimbine (an α(2)-adrenergic receptor antagonist) did not affect antinociception induced by hop extract in the writhing test. Our results suggest that hop extract shows an antinociceptive property in various pain models. Furthermore, the antinociceptive effect of hop extract may be mediated by opioidergic receptors, but not serotonergic and α(2)-adrenergic receptors.
Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 200-702, Korea.
Soo-Hyun
SH
Park
Yun-Beom
YB
Sim
Yu-Jung
YJ
Kang
Sung-Su
SS
Kim
Chea-Ha
CH
Kim
Su-Jin
SJ
Kim
Jee-Young
JY
Seo
Su-Min
SM
Lim
Hong-Won
HW
Suh