Astrocytes are required for the oscillatory activity in cultured hippocampal neurons.
Synchronous oscillations of intracellular calcium concentration ([Ca2+]i) and of membrane potential occurred in a limited population of glutamatergic hippocampal neurons grown in primary cultures. The oscillatory activity occurred in synaptically connected cells only when they were in the presence of astrocytes. Microcultures containing only one or a few neurons also displayed oscillatory activity, provided that glial cells participated in the network. The glutamate-transporter inhibitors L-trans-pyrrolidine-2, 4-dicarboxylic acid (PDC) and dihydrokainate, which produce an accumulation of glutamate in the synaptic microenvironment, impaired the oscillatory activity. Moreover, in neurons not spontaneously oscillating, though in the presence of astrocytes, oscillations were induced by exogenous L-glutamate, but not by the stereoisomer D-glutamate, which is not taken up by glutamate transporters. These data demonstrate that astrocytes are essential for neuronal oscillatory activity and provide evidence that removal of glutamate from the synaptic environment is one of the major mechanisms by which glial cells allow the repetitive excitation of the postsynaptic cell.
Verderio
C
C
CNR Cellular and Molecular Pharmacology and B. Ceccarelli Centers, Department of Medical Pharmacology, University of Milano, Italy.
Bacci
A
A
Coco
S
S
Pravettoni
E
E
Fumagalli
G
G
Matteoli
M
M
D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003998:Dicarboxylic Acids / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D007425:Intracellular Membranes / Q000378:metabolism; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009991:Oscillometry; D009994:Osmolar Concentration; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D013569:Synapses / Q000502:physiology
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D003998:Dicarboxylic Acids; D011759:Pyrrolidines; C103758:pyrrolidine-2,3-dicarboxylic acid; D018698:Glutamic Acid; C020889:dihydrokainic acid; D007608:Kainic Acid; D002118:Calcium