Fig. 10. Reversal of the effects of abdominal surgery on sucrose reinforcement by morphine. The number of sucrose pellets earned (  A ) and time required to earn the final pellet (  B ) are shown 24 h after laparotomy in animals given saline or morphine (mean ± SEM). Baseline data (BSL) are indicated for each group by the  vertical bars , with the  first bar representing the saline group, the  second bar representing the group given the lowest dose of morphine, and so forth. * Significantly different from baseline values,  P ≤ 0.05.