The antianalgesia induced by dextro-morphine or levo-morphine against levo-morphine-produced antinociception is mediated by glial stimulation in the mouse spinal cord E.T. Schwasinger, H.-E. Wu, J. Thompson, H.-S. Sun, M. Terashvili and L.F. Tseng1. 1Dept. of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226. We have previously demonstrated that the naturally occurring levo-morphine at a sub-analgesic picromolar dose or synthetic stereo-enantiomer dextro-morphine at a femtomolar dose pretreated intrathecally (i.t.) induces antianalgesia against levo-morphine-produced antinociception (Wu et al, JPET 310:240, 2004; Wu et al., SFN, 2005). Present study was then undertaken to determine if the antianalgesia induced by dextro-morphine or levo-morphine against levo-morphine-produced antinociception is mediated by the glial stimulation. The effect of the glial inhibitor propentofylline on the attenuation of the levo-morphine-produced tail-flick (TF) inhibition induced by dextro-morphine or levo-mor...