The Journal of Neuroscience, November 15, 2001, 21(22):8895-8905
Synchronous Oscillatory Activity in Immature Cortical Network Is
Driven by GABAergic Preplate Neurons
Thomas
Voigt,
Thoralf
Opitz, and
Ana D.
de Lima
Otto-von-Guericke Universität, Medizinische Fakultät,
Institut für Physiologie, 39120 Magdeburg, Germany
Neurons dissociated from embryonic cerebral rat cortex form a
differentiated network of synaptic connections and develop synchronous oscillatory network activity with the beginning of the second week
in culture. During an initial phase lasting 3-4 d, synchronous calcium transients can be blocked completely by either CNQX or bicuculline, showing that both glutamatergic and GABAergic neurons are
required for the generation of this form of activity. By manipulating dissociation and growth conditions, cultures containing different populations of GABAergic neurons were obtained. These cultures revealed
that a distinct population of large GABAergic neurons is a key element
in the generation of synchronous oscillatory network activity. A
minimal number of two large GABAergic neurons per square millimeter are
required for the occurrence of synchronous activity. Changes in the
density of all other types of GABAergic or non-GABAergic neurons has no
influence on the synchronous activity. Electron microscopic analysis
shows that the large GABAergic neurons form an interconnected network.
Exceptionally high somatodendritic innervation and extended axonal
arborization enable these neurons to collect electric network activity
and to distribute it effectively throughout the neuronal network.
Additional experiments indicated that most neurons developing in
culture to large GABAergic neurons are derived from the primordial
plexiform layer and reside in the subplate at the time of birth. We
suggest that they function as an integrating element that synchronizes
neuronal activity during early cortical development by collecting
incoming extrinsic and intrinsic signals and distributing them
effectively throughout the developing cortical plate.
Key words:
development; cerebral cortex; calcium; synchronous
activity; GABA; subplate
Copyright © 2001 Society for Neuroscience 0270-6474/01/21228895-11$05.00/0