2Department of Physiology, Aksaray University Faculty of Medicine, Aksaray, Türkiye
Abstract
Glutamate operates as the principal stimulator neurotransmitter in the mammalian central nervous system and is essential for cognitive functions, memory, and learning processes. It serves as a metabolic precursor of γ-aminobutyric acid (GABA) and is a constituent of the antioxidant glutathione. The glutamate-glutamine cycle regulates glutamate levels by facilitating its recycling between astrocytes and neurons. Glutamate is conveyed into synaptic vesicles by vesicular glutamate transporters (VGLUT) and is discharged into the synaptic cleft during neuronal depolarization. Extracellular glutamate is taken away from the synapse by excitatory amino acid transporters (EAAT), particularly those found in astrocytes, which help maintain glutamate homeostasis and prevent excitotoxicity. Glutamate receptors are fundamentally categorized into two primary classes: ionotropic (NMDA, AMPA, Kainate, Delta) and metabotropic. Ionotropic glutamate receptors (iGluRs) mediate fast excitatory responses, with N-methyl-D-aspartate (NMDA) receptors playing a key role in processes like synaptic plasticity and long-term potentiation (LTP) through calcium (Ca2+) influx. α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are crucial for rapid synaptic transmission and for the activation of NMDA receptors. Metabotropic receptors regulate intracellular signaling pathways via G-protein-coupled mechanisms. Dysfunction in the glutamate system is linked to various neurological disorders such as epilepsy, autism spectrum disorders, schizophrenia, and depression. Excess glutamate accumulation can lead to excitotoxicity and cell death. Furthermore, sex differences in glutamate levels may explain the varying impacts of neurological disorders across genders. Glutamate receptor agonists and antagonists present potential drug targets for treating glutamatergic system-related pathologies. Ketamine, memantine, riluzole, and D-cycloserine (DCS) are among the medicines employed in this domain. This review thoroughly analyzes the existing literature regarding the function of glutamate in the central nervous system. This review focuses on contemporary research on the association between glutamate receptors and neurological diseases. This study employs the literature review technique to offer a comprehensive perspective on the physiological and pathological roles of glutamate.