Browsing by Author "Maiju, Savolainen"

Myelin is a lipid-rich substance wrapped around nerve axons that can be adaptively modified in response to neuronal activity and experience. Recent research has revealed myelination of parvalbumin (PV) inhibitory interneurons, critical for brain oscillations and balance. Defects in PV interneuron myelination have been linked to psychiatric disorders, like schizophrenia. Tropomyosin receptor kinase B (TrkB) signaling has been shown to be important for myelination. Moreover, fluoxetine, an antidepressant, binds to TrkB receptors in PV interneurons, enhancing plasticity. While previous studies support the importance of PV interneuron mediated TrkB signaling for anti-depressant induced neural plasticity, its effect on PV interneuron myelination remains unexplored. The objective of this thesis was to investigate whether TrkB signaling, and fluoxetine affect the overall and PV-interneuron specific myelination in the medial prefrontal cortex (mPFC) in mice. Using immunohistochemical analysis, we assessed myelin changes through node of Ranvier morphology and myelin immunostaining intensity in control and in mice with heterozygous conditional TrkB deletion in PV interneurons (hereafter referred to as TrkB KO), with or without fluoxetine. We found that fluoxetine increases node length in TrkB KO mice, while reduced TrkB signaling shortens paranodes in PV neurons compared to controls. Our findings also depict that fluoxetine and PV-mediated TrkB signaling do not alter the overall myelination of the mPFC. The findings of this work provide mechanistic insights into PV interneuron myelination in the mPFC, with potential implications for demyelinating and psychiatric conditions where PV myelination plays a role.