Relationship between GABAergic interneurons migration and early neocortical network activity.

Available evidence converges to suggest that during the early development of the cerebral cortex, the emergence of the spontaneous network activity chronologically overlap with the end of the cell migration period in the developing cortex. We approached the functional regulation of neuronal migration in a culture model of neocortical networks, using time lapses to detect migratory movements, calcium-imaging to assess the activity of migratory neurons, and immunocytochemical methods to identify the migratory cells retrospectively. In cell cultures, early physiological development and cell migration are reproduced at a local network level, thus allowing the study of the interrelationships between cell migration and network development independent of the topographical complexity. Neurons migrate at least until 12 days in vitro and GABAergic neurons migrate faster compared with non-GABAergic neurons. A decline of migratory activity was coincident with the development of spontaneous synchronous network activity. Migrating interneurons did not participate in synchronous network activity, but interneurons that ended cell migration during observation time frequently engaged in synchronous activity within less than an hour. Application of GABA(A) and ionotropic glutamate receptor antagonists significantly increased the number of migrating GABAergic neurons without changing the dynamics of the migratory movements. Thus, neurotransmitters released by early network activity might favor the termination of neuronal migration. These results reinforce the idea that network activity plays an important role in the development of late-born GABAergic cells.