Spontaneous development of synchronous oscillatory activity during maturation of cortical networks in vitro.
Recent studies have focused attention on mechanisms of spontaneous large-scale wavelike activity during early development of the neocortex. In this study, we describe and characterize synchronous neuronal activity that occurs in cultured cortical networks naturally without pharmacological intervention. The synchronous activity that can be detected by means of Fluo-3 fluorescence imaging starts to develop at the beginning of the second week in culture and eventually includes the entire neuronal population about 1 wk later. A synchronous increase of [Ca(2+)](i) in the neuronal population is associated with a burst of action potentials riding on a long-lasting depolarization recorded in a single cell. It is suggested that this depolarization results directly from synaptic current, which was comprised of at least three different components mediated by AMPA, N-methyl-D-aspartate (NMDA), and GABA(A) receptors. We never observed a gradually depolarizing pacemaker potential and found no evidence for a change of excitability during inter-burst periods. However, we found evidence for a period of synaptic depression after bursts. Network excitability recovers gradually over seconds from this depression that can explain the episodic nature of spontaneous network activity. Using pharmacological manipulation to investigate the propagation of activity in the network, we show that synchronous network activity depends on both glutamatergic and GABA(A)ergic neurotransmission during a brief period. Reversal potential of GABA(A) receptor-mediated current was found to be significantly more positive than resting membrane potential both at 1 and 2 wk in culture, suggesting depolarizing action of GABA. However, in cultures older than 2 wk, inhibition of GABA(A) receptors does not result in block of synchronous network activity but in modulation of burst width and frequency.
Opitz
Thoralf
T
Department of Developmental Physiology, Institute for Physiology, Otto-von-Guericke University, 39120 Magdeburg, Germany. opitz@medizin.uni-magdeburg.de
De Lima
Ana D
AD
Voigt
Thomas
T
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D004594:Electrophysiology; D005456:Fluorescent Dyes; D018755:GABA Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018715:Microscopy, Video; D009415:Nerve Net / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014966:Xanthenes; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D018755:GABA Agonists; D014966:Xanthenes; C059715:Fluo-3; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002118:Calcium