Myelin, produced by oligodendrocytes (OLs), is a lipid-rich structure that wraps axons, facilitating the saltatory conduction and providing metabolic support to neurons. Myelin is a highly adaptable structure whose role in regulating synaptic transmission in the healthy and diseased brain have not been extensively examined and may be relevant for understanding neuronal dysfunctions associated with myelin-related disorders. Here, we investigated excitatory (EPSCs) and inhibitory (IPSCs) post-synaptic currents in layer IV of the somatosensory (barrel) cortex using a cuprizone-induced demyelination mouse model. First, Myelin Basic Protein (MBP) immunostainings showed a significant decrease during demyelination, and a partial recovery during remyelination. Functional studies employing whole-cell patch-clamp recordings of spiny stellate cells (SSC) in acute thalamocortical slices revealed an increase in the Excitatory/Inhibitory (E/I) ratio in demyelinated mice compared with controls. This imbalance was partially restored during remyelination. Furthermore, using paired recordings in Pvcre;tdTomatolox/+ mice, we tested the synaptic connectivity and paired-pulse ratio between parvalbumin (PV)-expressing interneuron-SSC unitary connections. Our results showed a decrease connectivity between these neurons in demyelinated mice. Moreover, a significant reduction of the frequency of miniature inhibitory postsynaptic currents (mIPSC) was observed in SSC under cuprizone condition, suggesting a decrease in presynaptic release during demyelination. Finally, immunostainings against PV showed no change in that PV interneuron density, excluding PV interneuron death. In conclusion, our findings provide deeper insight into how myelin influences the functionality of inhibitory synapses and highlighting its crucial role in maintaining the E/I balance in the somatosensory cortex.