title: Long-term culture of astrocytes attenuates the readily releasable pool of synaptic vesicles.
abstract: The astrocyte is a major glial cell type of the brain, and plays key roles in the formation, maturation, stabilization and elimination of synapses. Thus, changes in astrocyte condition and age can influence information processing at synapses. However, whether and how aging astrocytes affect synaptic function and maturation have not yet been thoroughly investigated. Here, we show the effects of prolonged culture on the ability of astrocytes to induce synapse formation and to modify synaptic transmission, using cultured autaptic neurons. By 9 weeks in culture, astrocytes derived from the mouse cerebral cortex demonstrated increases in β-galactosidase activity and glial fibrillary acidic protein (GFAP) expression, both of which are characteristic of aging and glial activation in vitro. Autaptic hippocampal neurons plated on these aging astrocytes showed a smaller amount of evoked release of the excitatory neurotransmitter glutamate, and a lower frequency of miniature release of glutamate, both of which were attributable to a reduction in the pool of readily releasable synaptic vesicles. Other features of synaptogenesis and synaptic transmission were retained, for example the ability to induce structural synapses, the presynaptic release probability, the fraction of functional presynaptic nerve terminals, and the ability to recruit functional AMPA and NMDA glutamate receptors to synapses. Thus the presence of aging astrocytes affects the efficiency of synaptic transmission. Given that the pool of readily releasable vesicles is also small at immature synapses, our results are consistent with astrocytic aging leading to retarded synapse maturation.
authors.affiliation: Department of Neuropharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawano
authors.forename: Shutaro
authors.initials: S
authors.lastname: Katsurabayashi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kakazu
authors.forename: Yuta
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Natsuko
authors.initials: N
authors.lastname: Kubo
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kubo
authors.forename: Hideto
authors.initials: H
authors.lastname: Okuda
authors.forename: Kotaro
authors.initials: K
authors.lastname: Takasaki
authors.forename: Kaori
authors.initials: K
authors.lastname: Kubota
authors.forename: Kenichi
authors.initials: K
authors.lastname: Mishima
authors.forename: Michihiro
authors.initials: M
authors.lastname: Fujiwara
authors.forename: N Charles
authors.initials: NC
authors.lastname: Harata
authors.forename: Katsunori
authors.initials: K
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D018920:Coculture Techniques; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008813:Mice, Inbred ICR; D018613:Microscopy, Confocal; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D017470:Receptors, Glutamate / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D005904:Glial Fibrillary Acidic Protein; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D001616:beta-Galactosidase