ИСТИНА

Brain cells are one of the most energy-demanding cell types in the body. Differences in metabolic profile and electron transport chain (ETC) structure of astrocytes and neurons have functional implications during conditions with varying oxygen supply (brain activity, hypoxia etc.) We assessed the redox state of the ETC of mitochondria with simultaneous analysis of blood oxygenation level in awake C57Bl/6 mice with Raman microspectroscopy. The mice expressed green fluorescent protein in astrocytes and near-infrared fluorescent protein in neurons following AAV injection and cranial window implantation in the somatosensory cortex (S1). Raman spectra recorded from astrocytes and neurons were used to quantify reduced C and B-type cytochromes. Raman spectra recorded from blood vessels were used to quantify oxyhaemoglobin in the blood. The relative amount of reduced cytochromes reversibly increased in astrocytes but not in neurons in response to animal activity: running on the trade-mill, grooming. Simultaneously the amount of oxyhaemoglobin has also increased. Thus, astrocytic mitochondria respond to local brain activity by ETC overloading with electrons, which may result in the production of reactive oxygen species.