Temporal and spatial evolution of various functional neurons during demyelination induced by cuprizone

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system (CNS). Here, we reported the temporal and spatial evolution of various functional neurons during demyelination in a cuprizone (CPZ)-induced mouse model. CPZ did not significantly induce the damage of axons and neurons after 2 weeks of feeding. However, after 4-6 weeks of CPZ feeding, axons and neurons were markedly reduced in the cortex, posterior thalamic nuclear group, and hippocampus. Simultaneously, the expression of TPH+ tryptophan neurons and VGLUT1+ glutamate neurons was obviously decreased, and the expression of TH+ dopaminergic neurons was slightly decreased in the tail part of the substantia nigra striatum, while the number of ChAT+ cholinergic neurons was not significantly different in the brain. In the second week of feeding, CPZ caused a higher level of glutamate secretion and up-regulated the expression of EAAT2 on astrocytes, which should contribute to rapid and sufficient glutamate uptake and removal. This finding reveals that astrocyte-driven glutamate retake protected the CNS from excitotoxicity by rapid re-uptake of glutamate in 4-6 weeks of CPZ feeding. At this stage, although NG2+ oligodendroglia progenitor cells (OPCs) were enhanced in the demyelination foci, the myelin sheath was still absent. In conclusion, we comprehensively observed the temporal and spatial evolution of various functional neurons. Our results will assist with understanding how demyelination affects neurons during CPZ-induced demyelination and provides novel information for neuroprotection in myelin regeneration and demyelinating diseases.