Astrocyte regulation of neural circuit activity and network states

Abstract

Astrocytes are known to influence neuronal activity through different mechanisms, including the homeostatic control of extracellular levels of ions and neurotransmitters and the exchange of signaling molecules that regulate synaptic formation, structure, and function. While a great effort done in the past has defined many molecular mechanisms and cellular processes involved in astrocyte‐neuron interactions at the cellular level, the consequences of these interactions at the network level in vivo have only relatively recently been identified. This review describes and discusses recent findings on the regulatory effects of astrocytes on the activity of neuronal networks in vivo. Accumulating but still limited, evidence indicates that astrocytes regulate neuronal network rhythmic activity and synchronization as well as brain states. These studies demonstrate a critical contribution of astrocytes to brain activity and are paving the way for a more thorough understanding of the cellular bases of brain function.

Astrocytic Neuroligins Are Not Required for Synapse Formation or a Normal Astrocyte Cytoarchitecture

“…In the gray matter of the cerebral cortex (Halassa et al 2007), hippocampus (CA1 S. radiatum) (Bushong et al 2001), and cerebellar cortex (Spacek 1985), astrocytes (or their cousins, the Bergmann glia in the cerebellum) occupy non-overlapping territories, effectively "tiling" the neuropil. Within their territories, astrocytes not only contact all other cells in brain, but also associate with axons and dendrites and ensheath synaptic junctions, thus forming tripartite synapses (Verkhratsky and Nedergaard, 2018;Saint-Martin and Goda, 2022;Oliveira and Araque, 2022;Lyon and Allen, 2022;Arizono and Nägerl, 2022). Astrocytes exhibit an exceptionally complex cytoarchitecture that includes thousands of fine processes infiltrating the neuropil where these processes likely perform multiple essential functions.…”

A lactate-dependent shift of glycolysis mediates synaptic and cognitive processes

“…Thus, our data are compatible with a scheme whereupon endogenous activation of astroglial CB1 receptors leads to acute increase of lactate, which in turn switches glycolysis towards serine production, ultimately providing the NMDAR activity necessary for novel object recognition. Astroglial CB1 receptors have been shown to control synaptic plasticity in different brain regions and to determine cognitive processes 12,14,[36][37][38] . The regulation of astrocyte calcium signaling is generally indicated as the cellular mechanism underlying these functions [39][40][41] .…”

Altered glial expression of the cannabinoid 1 receptor in the subiculum of a mouse model of Alzheimer's disease

“…Altogether, astroglial alteration in AD and functional changes associated with reactive astrocytes (Smit et al, 2021; Verkhratsky & Nedergaard, 2018) may have a direct impact on synaptic communication (Nanclares et al, 2021) and neuronal network function (Oliveira & Araque, 2022), which eventually would cause brain activity disruption and ultimately cognitive impairment (Escartin et al, 2019; Lines et al, 2022; Smit et al, 2021).…”