gliotransmitters

Gliotransmitters are signaling molecules released by glial cells that influence neuronal activity and synaptic transmission. In the concept of the tripartite synapse, astrocytes, a type of glial cell, actively participate in synaptic signaling by releasing gliotransmitters in response to neuronal activity. The term encompasses several chemically distinct messengers, most notably glutamate, D-serine, glycine, ATP, and GABA, among others. Astrocytic gliotransmitter release can occur via calcium-dependent exocytosis of vesicles, as well as through non-vesicular pathways such as transporter reversal, hemichannels formed by connexins, and pannexin channels. Microglia and, to a lesser extent, oligodendrocytes are also reported to release gliotransmitters, contributing to the signaling environment.

Gliotransmitters act on neuronal receptors including NMDA, AMPA, metabotropic glutamate receptors, purinergic P2X/P2Y receptors, and GABA receptors, thereby modulating synaptic transmission, timing, and plasticity. They participate in synaptic scaling and homeostatic regulation, and can influence neurovascular coupling and cerebral blood flow. They have been implicated in sleep regulation, learning, and memory processes.

Dysregulation of gliotransmission has been associated with pathological conditions such as epilepsy, chronic pain, neurodegenerative diseases, and neuroinflammation. However, the physiological significance and in vivo mechanisms remain active areas of research, with ongoing debates about the relative abundance and conditions under which gliotransmission dominates neuronal signaling.