RESUMO
Adjusting the thickness and internodal length of the myelin sheath is a mechanism for tuning the conduction velocity of axons to match computational needs. Interactions between oligodendrocyte precursor cells (OPCs) and developing axons regulate the formation of myelin around axons. We now show, using organotypic cerebral cortex slices from mice expressing eGFP in Sox10-positive oligodendrocytes, that endogenously released GABA, acting on GABAA receptors, greatly reduces the number of oligodendrocyte lineage cells. The decrease in oligodendrocyte number correlates with a reduction in the amount of myelination but also an increase in internode length, a parameter previously thought to be set by the axon diameter or to be a property intrinsic to oligodendrocytes. Importantly, while TTX block of neuronal activity had no effect on oligodendrocyte lineage cell number when applied alone, it was able to completely abolish the effect of blocking GABAA receptors, suggesting that control of myelination by endogenous GABA may require a permissive factor to be released from axons. In contrast, block of AMPA/KA receptors had no effect on oligodendrocyte lineage cell number or myelination. These results imply that, during development, GABA can act as a local environmental cue to control myelination and thus influence the conduction velocity of action potentials within the CNS. GLIA 2017;65:309-321.
Assuntos
Axônios/fisiologia , Córtex Cerebral/citologia , Bainha de Mielina/metabolismo , Oligodendroglia/fisiologia , Organogênese/fisiologia , Ácido gama-Aminobutírico/metabolismo , Animais , Axônios/efeitos dos fármacos , Axônios/ultraestrutura , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Córtex Cerebral/fisiologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , GABAérgicos/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Camundongos , Camundongos Transgênicos , Bainha de Mielina/ultraestrutura , Neurônios/citologia , Neurônios/efeitos dos fármacos , Oligodendroglia/efeitos dos fármacos , Oligodendroglia/ultraestrutura , Técnicas de Cultura de Órgãos , Organogênese/efeitos dos fármacos , Quinoxalinas/farmacologia , Receptores de GABA/genética , Receptores de GABA/metabolismo , Fatores de Transcrição SOXE/genética , Fatores de Transcrição SOXE/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genética , Tetrodotoxina/farmacologia , Ácido gama-Aminobutírico/farmacologiaRESUMO
Light is extensively used to study cells in real time (live cell imaging), separate cells using fluorescence activated cell sorting (FACS) and control cellular functions with light sensitive proteins (Optogenetics). However, photo-sensitive molecules inside cells and in standard cell culture media generate toxic by-products that interfere with cellular functions and cell viability when exposed to light. Here we show that primary cells from the rat central nervous system respond differently to photo-toxicity, in that astrocytes and microglia undergo morphological changes, while in developing neurons and oligodendrocyte progenitor cells (OPCs) it induces cellular death. To prevent photo-toxicity and to allow for long-term photo-stimulation without causing cellular damage, we formulated new photo-inert media called MEMO and NEUMO, and an antioxidant rich and serum free supplement called SOS. These new media reduced the detrimental effects caused by light and allowed cells to endure up to twenty times more light exposure without adverse effects, thus bypassing the optical constraints previously limiting experiments.