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. Author manuscript; available in PMC: 2022 Dec 1.
Published in final edited form as: Drug Alcohol Depend. 2021 Sep 24;229(Pt A):109101. doi: 10.1016/j.drugalcdep.2021.109101

Figure 4. Estrous cycle phase during the first treatment of high dose fentanyl (FTY) predicts later fentanyl preference in the conditioned place preference (CPP) paradigm.

Figure 4.

(A) Among the female rats administered low dose (4 μg/kg) or high dose (16 μg/kg) fentanyl-paired context, estrous phase (i.e., estrus vs. non-estrus) at initial fentanyl exposure during conditioning was predictive of subsequent fentanyl preference as a main factor. Post hoc analysis showed that the change in preference for the fentanyl-paired context in the CPP paradigm was significantly different between estrus and non-estrus groups in females given high dose fentanyl (*p < 0.05). Bar graphs display means ± SEM, with unique symbols representing individual estrous phases of females.