Summary of behavioral data.

Pain thresholds were measured before (pre-session) and after (post-session) the experimental session. The mean and standard deviation are given in degrees Celsius. The average ratings with standard error are in arbitrary units and categorized as non-painful (VAS < = 50) or painful (VAS >50) for each treatment condition (saline or naloxone). The average total number of stimuli for the particular category with standard deviation for each category is listed under No. of Stimuli.