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. 2022 Mar 17;13:841873. doi: 10.3389/fphar.2022.841873

FIGURE 5.

FIGURE 5

Effect of sex, estrous cycle phase, and dose on responding during reinstatement testing in female and male rats. Mean (±SEM) number of responses made on the lever formerly associated with fentanyl during the last extinction session versus the reinstatement session for males (A; left) and females (right) within the 0.25 (n = 8 males, n = 9 females), 0.75 (n = 8 males, n = 9 females), 1.5 (n = 8 males, n = 8 females), and 3.0 (n = 8 males, n = 7 females) dose (μg/kg) conditions and across all doses (B) (n = 29 males, n = 29 females). (+) Significantly higher responding in the reinstatement session compared with the last extinction session. (^) Significantly higher responding in estrus females compared with non-estrus females.