Perinatal Fluoxetine Exposure Has No Major Effect on Myelin-Associated Glycoprotein and Myelin Basic Protein Levels in Auditory Brain Regions

Hearing loss and serotonergic dysfunction both impact social and cognitive behaviors, yet their neurobiological interplay remains poorly understood. This study investigated whether perinatal fluoxetine exposure alters myelination in (auditory) brain regions during development. Female Wistar rats received 10 mg/kg fluoxetine from gestational day 1 until postnatal day (PND)21. Brain tissue was collected from male offspring at PND21 and PND35. Myelination was assessed via immunohistochemical analysis of Myelin-Associated Glycoprotein (MAG) and Myelin Basic Protein (MBP) in the auditory cortex, inferior colliculus, and corpus callosum. MAG+ cell counts, MBP+ area, and MBP fluorescence intensity were quantified. No major effects of fluoxetine were observed on myelin markers in any brain region or developmental stage. However, changes in myelination emerged between PND21 and PND35. MAG+ cell density declined in the inferior colliculus but remained stable in the auditory cortex. MBP+ area decreased over time in both the corpus callosum and auditory cortex, while MBP fluorescence intensity increased in the corpus callosum. These results suggest that myelination changes between PND21 and PND35 are region- and age-dependent and not altered by fluoxetine. These findings highlight the dynamic nature of postnatal myelination and suggest that serotonergic alterations alone may be insufficient to disrupt structural maturation in auditory regions.