FIGURE 2.

Body weight in male and female rats over the course of morphine injections, withdrawal, and oxycodone SA. A, Vehicle‐treated, but not morphine‐treated, male rats gain weight during the 12d morphine/vehicle injection regimen. Female rats, regardless of treatment, gain a nominal amount of weight. Inset (dashed box): A daily pattern of weight changes emerges at the end of the 12d morphine injection regimen. Morphine‐treated male and female rats gain a small amount of weight during the day (from AM to PM measurements), whereas vehicle‐treated rats tend to lose a small amount of weight during the day. N = 25–33 per group. Each day shows body weights prior to the two injections: White background is AM injection, grey background is PM injection. B, Body weights remain significantly decreased in morphine‐treated male rats on withdrawal days 3, 4, and 5, although weights tend to be lower in morphine‐withdrawn males throughout the withdrawal period. No change in body weights is observed in female rats during withdrawal. N = 25–33 per group. C, Body weights of male rats previously exposed to morphine remain qualitatively lower throughout the oxycodone SA tests, but oxycodone SA does not in itself alter body weights in either males or females. N = 15–18 per group. *p < 0.05, **p < 0.01 comparing within‐sex body weights on specific days or between two timepoints indicated by brackets; ^{^^} p < 0.01 main effect of sex