Fig. (1).

Mechanisms of astrocyte-mediated glutamate regualtion. Astrocytes are intricately involved in glutamate regulation through several mechanisms. Excitatory amino acid transporter-2 (1, EAAT-2) is responsible for uptake of extracellular glutamate into the cell, where intracellular glutamine synthetase (2, GS) catalyzes the reaction forming glutamine from glutamate. Glutaminase (3, GLS) catalyzes the reaction to convert glutamine to glutamate where astrocytes can package it into vesicular glutamate transporters (4, VGLUT-1). The expression of functional metabotropic glutmate receptors (5, mGluRs) allows glutamate signaling leading to increased intracellular calcium levels.