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Levonorgestrel Androgenic Effects and the Delay of Habit Development in Female Rats
Firehock, Grace C.
Firehock, Grace C.
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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.
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2025-01-01