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. 2021 Jul 6;15:648860. doi: 10.3389/fnsys.2021.648860

Figure 2.

Figure 2

Energetic and oxygen costs and coupling of neural processing. (A) Neurovascular and neurometabolic coupling. Physiological changes in the neural activity of the brain are invariably accompanied by changes in local blood flow and glucose utilization. During the modality-specific activation of a brain region, glutamate release from active synapses induces the increase of glucose use and lactate production of perivascular astrocytes and an increase in cerebral blood flow (CBF) through receptor-mediated nitric oxide (NO) formation. These activity-dependent processes help neurons to meet their energy needs. (B) Pharmacological analysis reveals an energy budget in which 11% of O2 use is on presynaptic action potentials (APs), 17% is on presynaptic Ca2+ entry and transmitter release, 46% is on postsynaptic glutamate receptors, and 26% is on postsynaptic APs, is approximately accordance with theoretical brain energy budgets. (C) Most of neurons and synapses (90%) in the cerebral cortex are either glutamatergic or gamma-aminobutyric acid-ergic (GABAergic) while 75% of the total cortical energy consumption is coupled to glutamate (60%) and GABA neurotransmitter cycling (left). Specially, the energy consumption used for glutamatergic neurotransmission (right) includes various neuronal components underlying the neural activity: presynaptic AP, entry of presynaptic Ca2+ ions, neurotransmitter recycling (release, uptake, conversion, and storage in vesicles), and postsynaptic AP.