Pseudoginsenoside-F-11 attenuates morphine-induced signalling in Chinese hamster ovary-mu cells

Pseudoginsenoside-F-II (PFII), an ocotillol type saponin isolated from Pana x quinquefolium L., has been shown to antagonize the behavioral actions of morphine. Biochemical experiments revealed that PFII could inhibit diprenor phine (DIP) binding with an IC50 of similar to6.1 muM and reduced the bindi ng potency of morphine in Chinese hamster ovary (CHO)-mu cells. Furthermore , PFII significantly attenuated morphine-stimulated [S-35]GTP gammaS bindin g in a dose dependent manner, and strongly decreased the efficacy of morphi ne to inhibit intracellular cAMP production. In addition, PFII pretreatment could also significantly inhibit naloxone induced cAMP overshoot in the mo rphine-pretreated cells. However, PFII per se had no effect on either [S-35 ]GTP gammaS binding or intracellular cAMP accumulation. These data suggeste d that PFII antagonized the morphine stimulated opioid receptor signalling directly at the cellular level. NeuroReport 12:1453-1456 (C) 2001 Lippincot t Williams & Wilkins.