Pharmacological Study on the Novel Antinociceptive Agent, a Novel Monoterpene Alkaloid from Incarvillea sinensis

To determine the antinociceptive mechanism of incarvillateine (INCA), the opiate antagonists nor-binaltorphimine (nor-BNI), β-funaltrexamine (β-FNA) and naltrindole (NTI) were pretreated prior to its injection in a formalin test. The antinociceptive effect of INCA was antagonized by nor-BNI (κ-receptor antagonist) and β-FNA (μ-receptor antagonist), while NTI (δ-receptor antagonist) did not influence its effect. Furthermore, the antinociceptive effect of INCA was blocked by theophylline (THEO), an adenosine-receptor antagonist. These results suggested that the antinociceptive effect arose from the activation of μ-, κ-receptors and adenosine-receptor.