rats were placed on a progressive-ratio operant schedule as well; such that the 25, 50 and 100 mg/kg doses were effective in P and sP rats, but none of the doses were effective in AA rats. Regarding latency to respond, the 100 mg/kg dose of GS39783 increased the latency to respond under the fixed-ratio schedule in the P and AA, but not sP, rat lines. However, none of the GS39783 doses affected latency to respond under the progressive-ratio condition. It should be noted that baclofen continues to be examined in clinical trials (Litten et al., 2012).
