Date of Completion

2025

Document Type

Honors College Thesis

Department

Neuroscience

Thesis Type

Honors College, College of Arts and Science Honors

First Advisor

Donna Toufexis

Keywords

habit, goal-directed, behavior, female rats, androgen, progestin

Abstract

Hormonal contraceptives are used by millions of women worldwide; however, there is extremely limited research on their cognitive and behavioral side effects. Levonorgestrel (LNG) is a widely used synthetic progestin found in many types of female hormonal contraceptives. LNG has recently been found to delay habit development in intact female rats, suggesting it may influence learning and decision-making processes. Habitual behavior is characterized by automatic actions that continue even when the outcome is no longer valuable, unlike goal- directed behavior, which is flexible and outcome-sensitive. The underlying mechanism driving LNG’s behavioral effects is not yet understood, but one potential explanation is that LNG’s androgenic properties contribute to its impact on habit development. In this study, female rats were implanted with either slow-releasing LNG or cholesterol (control) filled capsules. In addition, subsets of the animals received subcutaneous injections of flutamide, an antiandrogen, or a vehicle control. All rats underwent a series of behavioral assessments, including reward devaluation, to evaluate for habit formation or goal-directed behavior. The rats that received both LNG and flutamide exhibited habitual behavior, while those receiving LNG with the flutamide vehicle displayed some goal-directed patterns. These findings suggest that flutamide plays a role in the effects LNG has on habit formation, potentially implicating androgenic signaling in the regulation of instrumental learning behaviors. This prompts further investigation into the cognitive implications and neuroendocrine mechanisms of LNG.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Available for download on Tuesday, June 01, 2027

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