Gonadal Steroid Hormones Impact Perineuronal Net Density in an Age- Dependent Manner in the Medial Prefrontal Cortex of Mice

Adolescence is a key developmental period in which brain and behavioral changes coincide with pubertal onset and the secretion of gonadal steroid hormones. The brain's ability to reorganize and respond to stimuli, also known as neuroplasticity, is regulated by perineuronal nets (PNNs). PNN density increases across adolescence in the medial prefrontal cortex (mPFC); however, it remains unclear whether secretions of gonadal steroid hormones during puberty influence PNN development in the mPFC. The current study investigates if PNN density is regulated by hormones, age, or an interaction between these factors. To distinguish between these possibilities, male and female C57 mice were gonadectomized prior to the onset of puberty. After gonadectomy, males were administered testosterone and females were administered estradiol either prepubertally (P23), during adolescence (P40), or in adulthood (P63). Brains were collected after one week of steroidal hormone treatment. The prelimbic (PL) (A32) and infralimbic (IL) (A25) subregions of the mPFC were imaged on an immunofluorescent Keyence microscope, and the number of PNNs were counted. In the PL (A32) subregion, both male and female hormone-treated animals displayed an increase in PNN density only during adolescence and adulthood. These data suggest that gonadal steroid hormones regulate PNN development in an age-dependent manner. In contrast, no effects of hormone or age were observed in the IL (A25) subregion. These data may have implications for the increased mental health risks associated with early or late pubertal timing in humans.