Evolution of Astrocyte-Neuron Interactions Across Species.

Proper functioning of the central nervous system depends on various tightly regulated phenomena, among which astrocyte-neuron interactions are of critical importance. Various studies across the species have highlighted the diverse yet crucial roles of astrocytes in regulating the nervous system development and functions. In simpler organisms like worms or insects, astrocyte-like cells govern basic functions such as structural support to neurons or regulation of extracellular ions. As the species complexity increases, so does the functional and morphological complexity of astrocytes. For example, in fish and amphibians, these cells are involved in synaptic development and ion homeostasis, while in reptiles and birds, astrocytes regulate synaptic transmission and plasticity and are reported to be involved in complex behaviors. Other species like those belonging to mammals and, in particular, primates have a heterogeneous population of astrocytes, exhibiting region-specific functional properties. In primates, these cells are responsible for proper synaptic transmission, neurotransmitter release and metabolism, and higher cognitive functions like learning, memory, or information processing. This chapter highlights the well-established and somewhat conserved roles of astrocytes and astrocyte-neuron interactions across the evolution of both invertebrates and vertebrates.