Age-dependent remodelling of ionotropic signalling in cortical astroglia.

Cortical astrocytes express fast ionotropic receptors for glutamate and ATP, although their role in neurone-glia communication remains controversial. Stimulation of neuronal afferents in mice neocortex triggers complex glial synaptic currents (GSCs) mediated by NMDA, P2X and AMPA receptors and glutamate transporters. In addition, astrocytes demonstrate spontaneous 'miniature' GSCs resulting from quantal release of neurotransmitters. Here, we demonstrate that maturation and aging of the brain of mice (from 1 to 21 months) affect the density of ionotropic receptors in astrocytes and their role in GSCs generation. The AMPA-receptor-mediated component is the largest in young animals and progressively declines with age. The P2X and NMDA components of GSC are smallest in young, maximal in adult (3 and 6 months old) and once more decrease in old mice, probably reflecting the remodelling of neuronal-glial circuitry. Our results demonstrate that fast synaptic transmission between neurones and astrocytes in neocortex that may be involved in information processing in neuronal-glial networks undergoes remodelling during brain maturation and aging.