Glial modulation of synaptic transmission: Insights from the supraoptic nucleus of the hypothalamus.
Astrocytes clear synaptically released glutamate from the extracellular space through high-affinity transporters present on their plasma membrane. By controlling the extracellular level of the main excitatory transmitter in the central nervous system, astrocytes thus contribute prominently to the regulation of overall cellular excitability and synaptic information processing. We recently investigated the influence of the glial environment on glutamatergic and GABAergic neurotransmission in the supraoptic nucleus of the rat hypothalamus under physiological conditions such as lactation that significantly reduce astrocytic coverage of its neurons. By performing electrophysiological analyses on this unique model of dynamic neuronal-glial interactions, we have been able to show that the fine astrocytic processes normally enwrapping synapses serve two important functions. First, they govern the level of activation of presynaptic metabotropic glutamate receptors on glutamatergic terminals, thereby regulating synaptic efficacy at excitatory synapses. Second, they act as a physical and functional barrier to diffusion in the extracellular space, limiting spillover of glutamate and other neuroactive substances and therefore contributing to the regulation of heterosynaptic transmission and intercellular communication.
Oliet
Stéphane H R
SHR
INSERM U378, Institut François Magendie, Université Victor Segalen Bordeaux 2, Bordeaux, France.
Piet
Richard
R
INSERM U378, Institut François Magendie, Université Victor Segalen Bordeaux 2, Bordeaux, France.
Poulain
Dominique A
DA
INSERM U378, Institut François Magendie, Université Victor Segalen Bordeaux 2, Bordeaux, France.
Theodosis
Dionysia T
DT
INSERM U378, Institut François Magendie, Université Victor Segalen Bordeaux 2, Bordeaux, France.
D000818:Animals; D001253:Astrocytes / Q000502:physiology* / Q000648:ultrastructure; D002450:Cell Communication / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D013495:Supraoptic Nucleus / Q000502:physiology* / Q000648:ultrastructure; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018094:Receptors, Metabotropic Glutamate; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid