Fig. 1. Comparison of behavioral effects produced by subcutaneous administration of butorphanol and morphine. (  A ) Dose–response curve for itch/scratching responses. (  B ) Dose–response curve for antinociception against 50°C water. Behavioral responses were determined using a cumulative dosing procedure. Each value represents mean ± SEM (n = 6).  Symbols represent different dosing conditions for the same monkeys. * Significant difference from the vehicle condition (  P < 0.05).