Effects of ginsenosides injected intrathecally or intracerebroventricularly on antinociception induced by morphine administrated intracerebroventricularly in the mouse.

1. Total saponin fraction at doses of 0.1 to 1.0 microgram, which administered IT alone did not affect the latencies of the tail-flick threshold, dose dependently attenuated inhibition of the tail-flick response induced by ICV-administered morphine (2 micrograms). 2. Total saponin fraction at doses of 1 to 20 micrograms, which administered ICV alone did not affect the latencies of the tail-flick response, did not affect ICV-administered morphine-induced antinociception. 3. The duration of antagonistic action of the total saponin fraction against morphine-induced antinociception lasted for at least 6 hrs. 4. Various doses of ginsenosides Rb2, Rc, Rd and Rg1, but not Rb1 and Re, injected IT dose dependently attenuated antinociception induced by morphine administered ICV. 5. In summary, ginsenosides Rb2, Rc, Rd and Rg1 injected spinally appear to have antagonistic action against the antinociception induced by supraspinally applied morphine. On the other hand, the total ginseng fraction, at supraspinal sites, may not have an antagonistic action against the antinociception induced by morphine administered supraspinally.