Development of low magnesium-induced spontaneous synchronized bursting and GABAergic modulation in cultured rat neocortical neurons.

Abstract Development of spontaneous synchronized bursting in the early stages of rat neocortical neuronal cultures was studied by whole-cell and extracellular recordings. Neocortical neurons from rat embryos were cultured on planar electrode arrays, and low Mg 2+ -induced spontaneous activity was recorded from 5 to 16 days in vitro (DIV). At 5–6 DIV the current synchronized to the bursting had only a slow component lasting 3–5 s, whereas in older cultures a fast transient component was dominant. A γ-aminobutyric acid (GABA) A receptor antagonist, bicuculline methiodide, had little effect on the spontaneous activity at 5–6 DIV, whereas in older cultures it had a marked effect on the slow current component. These results suggest a role of GABAergic transmission in the development of synchronized activities.