Continuous versus intermittent theta burst stimulation in the treatment of experimental autoimmune encephalomyelitis: a glutamate transporters study

Background: Synaptic overload with glutamate aggravates neurotransmission and worsen the progression of the neurodegenerative disease, such as multiple sclerosis (MS). The experimentally induced autoimmune encephalomyelitis (EAE) in rats is a well-established animal model to study MS. Glutamate reuptake occurs by glial glutamate transporter (GLT-1), and glutamate-aspartate transporter (GLAST) localized predominantly in astrocytes terminals. The focus of the study addressing the expression of these transporters in EAE rats and those subjected to theta burst stimulation (TBS), that promotes long-lasting modulation of neuronal activity in rats/humans. Leading by the reported outcomes of TBS, we examined if TBS underlying mechanisms refer to astroglial glutamate transporters status.Methods : We studied changes in the expression of glial glutamate transporter GLT-1 and glutamate-aspartate transporter (GLAST), and glial fibrillary acidic protein (GFAP), in the spinal cord of EAE rats, subjected to intermittent (iTBS) and continuous (cTBS) theta burst stimulation. We quantified the expression of GLAST, GLT-1, and GFAP by immunofluorescence in control and experimental groups of Dark Agouti rats.Results: EAE elevated expression of GFAP, GLAST, and GLT-1. Both TBSs reduced the expression of GFAP. Continual TBS did not interfere with glutamate transporters in EAE rats, while iTBS decreased GLT-1, and increased GLAST.Conclusion: Continual TBS reduced astrogliosis more efficiently than iTBS, in EAE rats. Besides, it did not mitigate the glutamate transporters' expression; thus, glutamate reuptake remained upraised in cTBS exposed EAE rats. Accordingly, we concluded that cTBS might advance the remyelination of damaged neuronal cells in EAE rats. The future clinical trials on the treatment of MS may consider the data of this pre-clinical animal study.