Figure 2. Canine gastrocnemius muscle paralysis versus the effect site concentration of metocurine among dogs with long-term conditioning exercise, healthy dogs, and dogs with either hind limb cast immobilization or disuse atrophy instituted by deep sedation in the intensive care unit. The concentration associated with 50% diminution of the twitch (IC50) for each study differs from its pretreatment normal value. Data are from the current study and from work by Fung et al. [7]and Gronert et al. [11]The curve from healthy dogs represents pooled control values taken at the beginning of each study (see text for details). Mean metocurine IC50values and slope factors used to generate these curves include exercise: 114 ng/ml, [Greek small letter gamma] 2; normal: 255 ng/mL, [Greek small letter gamma] 5.6; casted hind limb disuse: 735 ng/ml, [Greek small letter gamma] 5.1; and intensive care unit disuse: 1,716 ng/ml, [Greek small letter gamma] 2.