Antinociception, tolerance and withdrawal symptoms induced by 7-hydroxymitragynine,
an alkaloid from the Thai medicinal herb Mitragyna speciosa
Kenjiro Matsumotoa, Syunji Horiea,Hiromitsu Takayamab, Hayato Ishikawab, Norio Aimib, Dhavadee Pongluxc, Toshihiko Murayamad and Kazuo Watanabed.
Laboratory of Pharmacolgy, Faculty of Pharmaceutical Sciences, Josai International University, Japan
Laboratory of Molecular Structure and Biological Function, Graduate School of Pharmaceutical Sciences, Chiba University, Japan. Faculty of Pharmaceutical Sciences, Chulalongkorn University, Thailand
19 June 2004

Abstract
7-Hydroxymitragynine is a potent opioid analgesic alkaloid isolated from the Thai medicinal herb Mitragyna speciosa. In the present study, we investigated the opioid receptor subtype responsible for the analgesic effect of this compound. In addition, we tested whether development of tolerance, cross-tolerance to morphine and naloxone-induced withdrawal signs were observed in chronically 7-hydroxymitragynine-treated mice.

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EFFECT OF CAFFEINE AND CODEINE ON ANTINOCICEPTIVE ACTIVITY OF ALKALOID EXTRACT FROM LEAVES OF KRATOM (MITRAGYNA SPECIOSA KORTH.)
Ornchuma Botpiboon, Sathaporn Prutipanlai, Benjamas Janchawee,Sittipoom Thainchaiwattana.
Songkla University, Thailand
Regional Forensic Science Songkhla, Thailand
2007 

Abstract:
In this study, the effects of caffeine and codeine on antinociceptive activity of an alkaloid extract from leaves of M. speciosa using hot plate test were examined in rat model. The results were found that single oral administration of alkaloid extract at the dose of 100 mg/kg significantly increased latency of nociceptive response at 30, 60, 90 and 120 minutes in the heat induced pain in rats when compared with control vehicle group (p < 0.05).

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