THE INFLUENCE OF ESTROGEN ON CONDITIONED CONTEXT AVERSION LEARNING

Date

2024-7

Author

Akgül, Cemile Ceren

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Anticipatory nausea and vomiting (ANV) are distressing side effects of chemotherapy, hindering patients from adhering to treatment. ANV involves nausea in anticipation of chemotherapy, developed through classical conditioning. While ANV is more prevalent in women than in men, preclinical studies are scarce and focused on males. The limited literature on the sex differences in animal model of ANV, conditioned context aversion (CCA), also shows enhanced conditioned response in females, possibly explained by female gonadal hormones. The present study investigates the cause of sexual dimorphism observed in ANV through a CCA procedure in which female CD1 mice associate a distinctive context with LiCl. In Experiment 1, the influence of ovarian hormones is investigated by comparing the aversion levels of ovariectomized and sham-operated mice. The results show that ovariectomized mice extinguished faster than sham-operated mice. Experiment 2 examined the role of estradiol in prolongation of extinction in intact females. To this end, subjects were ovariectomized and half of them were administered estradiol while the remaining were administered oil to control. While estradiol-administered animals maintained aversion for a single retention trial in Experiment 2, control animals did not exhibit an aversion. The results of Experiment 1 show that ovarian-secreted hormones facilitate CCA. On the other hand, estradiol administration in Experiment 2 partially rescued the impact of the ovariectomy either due to the inefficiency of estradiol itself, or the hormone treatment method. Overall, the experiments suggest that the ovarian-secreted hormones facilitate CCA in mice which can explain observed sex differences in ANV in humans.

Subject Keywords

anticipatory nausea, conditioned context aversion, mice, estrogen

URI

https://hdl.handle.net/11511/110098

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Graduate School of Social Sciences, Thesis