title: Plasticity of astrocytic coverage and glutamate transporter expression in adult mouse cortex.
abstract: Astrocytes play a major role in the removal of glutamate from the extracellular compartment. This clearance limits the glutamate receptor activation and affects the synaptic response. This function of the astrocyte is dependent on its positioning around the synapse, as well as on the level of expression of its high-affinity glutamate transporters, GLT1 and GLAST. Using Western blot analysis and serial section electron microscopy, we studied how a change in sensory activity affected these parameters in the adult cortex. Using mice, we found that 24 h of whisker stimulation elicited a 2-fold increase in the expression of GLT1 and GLAST in the corresponding cortical column of the barrel cortex. This returns to basal levels 4 d after the stimulation was stopped, whereas the expression of the neuronal glutamate transporter EAAC1 remained unaltered throughout. Ultrastructural analysis from the same region showed that sensory stimulation also causes a significant increase in the astrocytic envelopment of excitatory synapses on dendritic spines. We conclude that a period of modified neuronal activity and synaptic release of glutamate leads to an increased astrocytic coverage of the bouton-spine interface and an increase in glutamate transporter expression in astrocytic processes.
authors.affiliation: Départment de Biologie Cellulaire et de Morphologie, Lausanne, Switzerland.
authors.forename: Christel
authors.initials: C
authors.lastname: Genoud
authors.forename: Charles
authors.initials: C
authors.lastname: Quairiaux
authors.forename: Pascal
authors.initials: P
authors.lastname: Steiner
authors.forename: Harald
authors.initials: H
authors.lastname: Hirling
authors.forename: Egbert
authors.initials: E
authors.lastname: Welker
authors.forename: Graham W
authors.initials: GW
authors.lastname: Knott
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000502:physiology*; D002540:Cerebral Cortex / Q000378:metabolism*; D049229:Dendritic Spines / Q000378:metabolism / Q000502:physiology; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D051379:Mice; D008813:Mice, Inbred ICR; D008954:Models, Biological; D009473:Neuronal Plasticity / Q000502:physiology*; D017729:Presynaptic Terminals / Q000378:metabolism / Q000502:physiology; D009435:Synaptic Transmission; D014738:Vibrissae / Q000294:innervation
chemical_list: D027322:Amino Acid Transport System X-AG; D027342:Excitatory Amino Acid Transporter 2