ИСТИНА

Neurons and astrocytes are among of the most energy-demanding cell types in the body. They are known to have differences in the metabolic profile and in the electron transport chain (ETC) structure. Here, we assessed the redox state of the ETC of mitochondria in two cell types with simultaneous analysis of blood oxygenation level in awake C57Bl/6 mice with label-free Raman microspectroscopy. The mice expressed green fluorescent protein in astrocytes and near infrared protein in neurons for cell type identification; and HyPer7 to monitor H2O2level in mitochondria matrix of astrocytes and neurons, following AAVs injections 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 amount of oxyhaemoglobin increased in both venules and arterioles during locomotion. The relative amount of reduced cytochromes reversibly increased in astrocytesand decreased in neurons in response to animal activity: running on the trade-mill or grooming. The overloading of astrocytes ETC with electrons was accompanied by the production of H2O2 in the mitochondria matrix but not in neurons indicating reactive oxygen species (ROS) generation in ETC of astrocytes. Our results demonstrate that astrocytes and neurons differentially change mitochondria redox state in response to physiological activity. This leads to ROS generation in mitochondria matrix of astrocytes which possibly play a signalling function providing another mechanism of communication between astrocytes and other cells in the brain active milieu.