Figure 1.

I. Overview of different substrates obtained from glucose: (A) Glucose is transported from capillaries through GLUT1 and (B) into the neuron via GLUT3 or into the astrocytes through GLUT1. (C) In astrocytes glucose can also be obtained from glycogen reserves to then be transformed into pyruvate which enters into the mitochondria where cellular respiration takes place. The neuron can utilize glucose from blood or lactate, (D) transported from the astrocytes to get the pyruvate. (E) Neurons can also uptake other metabolites like alanine, oleic acid, ketone bodies and α-ketoglutarate from astrocytes. II. Regulation of the blood flow through the release of molecular mediators by astrocytes (F). III. Ions and K⁺ Uptake. (G) In normal conditions, astrocytes are involved in “spatial buffering” of K⁺ and proton shuttling, for this purpose they have Na⁺/H⁺ exchangers, bicarbonate transporters, monocarboxylic acid transporters, and the vacuolar-type proton ATPase in their membrane. (H) After ischemia, lack of energy leads to the release of potassium into the extracellular space and entry of sodium into cells, this causes neuronal plasma membrane depolarization. Abbreviations: ETS, Electron Transport System; a-KG, α-ketoglutarate; LAC, Lactate; Pyr, Pyruvate; TCAC, Tricarboxylic acid cycle; LDH, Lactate Dehydrogenase; ALA, Alanine; GLC, Glucose; K⁺, potassium; Na⁺, sodium; H⁺, proton.