Intercellular Junctions

Glial cells do not make chemical synapses with other cells, but they often form gap junctions with neighboring glial cells to create an electrochemical syncytium. The aqueous pore of the gap junction channel, formed by hexameric assemblies of proteins (connexins) in the apposed membranes of adjoining cells (Fig. 1.7A), permit the passage of ions, metabolites, and other small molecules (< 1 kDa). Although intercellular junctional complexes of various types, including gap junctions, are often...

Reactive Gliosis

The vertebrate CNS is remarkable for its morphological complexity and functional sophistication. Therefore, it is surprising that such a highly evolved system lacks efficient repair mechanisms for neuronal regeneration and functional recovery following trauma. Many factors are responsible for the limited regenerative capacity of the mammalian CNS. For example, there may be an inability to reinitiate critical steps that occur during normal development, which are dependent upon expression of...

C

Glutamate stimulates glucose uptake by glia. A. A concentration-response curve showing stimulation of 3H 2DG uptake by astrocyte cultures. B. Glutamate-stimulated 3H 2DG uptake is inhibited by ouabain. Histogram shows 3H 2DG uptake in glutamate-treated (hatched bars) or untreated (solid bars) cultures in the absence (control) or presence of Ouabain. C. Schematic of the mechanism for glutamate-induced glycolysis in astrocytes during physiological activation. At glutamatergic...

Metabolic Interactions with Neurons

Glial cells have long been considered as providers of glucose and other nutrients to neurons (Golgi, 1886). This idea stems from the observation that, in the brain, glycogen granules are normally found in glial cells. Furthermore, because glial processes are interspersed among brain capillaries and neurons, it was thought that they served as a conduit for passage of glucose from capillaries to neurons. Early experimental evidence for metabolic coupling between neurons and glial cells came from...