The effects of artificially induced proestrus on heroin intake: A critical role for estradiol.

Abstract

This study demonstrates that estradiol decreases heroin intake, suggesting that estrogen-based pharmacotherapies may be beneficial to women with opioid use disorders.

The Effects of Strain and Estrous Cycle on Heroin- and Sucrose-Maintained Responding in Female Rats

“…However, more recent studies have reported that estradiol reduces heroin seeking across multiple experimental conditions (Sedki et al, 2015;Vazquez et al, 2020). Results from our laboratory are consistent with these most recent studies, given that we have shown that opioid self-administration is reduced during proestrus in an estrogen but not progesterone dependent manner (Lacy et al, 2016;Smith et al, 2020a;Smith et al, 2020b). Similar processes are likely responsible for the reduction in heroin-maintained responding in the present study.…”

“…Approximately one week after surgery, rats were transferred to heroin self-administration chambers that served as home cages during drug self-administration testing. At this time, estrous phase monitoring began as described previously (Lacy et al, 2016; Smith et al, 2020b). Briefly, approximately one hour prior to the start of each self-administration session, samples of vaginal cells were obtained via vaginal lavage and examined under light microscope to classify as metestrus, diestrus, proestrus, or estrus.…”

“…Briefly, approximately one hour prior to the start of each self-administration session, samples of vaginal cells were obtained via vaginal lavage and examined under light microscope to classify as metestrus, diestrus, proestrus, or estrus. Across multiple studies (Lacy et al, 2016; Smith et al, 2020a; Smith et al, 2020b), we have seen no differences between metestrus and diestrus on heroin intake, so data from these phases were combined for analysis.…”

“…Approximately one week after surgery, rats were transferred to heroin self-administration chambers that served as home cages during drug self-administration testing. At this time, estrous phase monitoring began as described previously (Lacy et al, 2016;Smith et al, 2020b).…”

“…Previously, our laboratory reported a decrease in heroin self-administration during the proestrus phase of the female estrous cycle (Lacy et al, 2016, Smith et al, 2020a; Smith et al, 2020b). Consistently, we observed a reduction in heroin intake between 55% and 70% compared to sessions during other phases of the estrous cycle.…”