Analgesic effects and non-dependence of ipalbidine

Ipalbidine is a photoactive alkaloid isolated from the seeds of Ipomoea hardwickii Hemsl. The analgesic effects of ipalbidine were determined by 3 methods (mouse hot plate; mouse writhing body and tail flick). Their EDso were 21.6, 27.6 and 63.2 mg/kg, respectively. The analgesic effect of ipalbidine was demonstrated by using the rabbits K+ permeation method. The analgesic effect of ipalbidine in mice was not antagonized by naloxone. In physical dependent test. no jumping was observed in mice and no reduction of body weight was observed in rats treated with ipalbidine. In the subtitution test of rats depended on morphine, ipalbidine did not substitute morphine. Opioid receptor competitive binding assay showed that ipalbidine did not displace the binding of [3H]etorphine. These results indicated that ipalbidine is a non-addictive analgesic.