Synchronization of action potentials during low-magnesium-induced bursting

The relationship between mono- and polysynaptic strength and action potential synchronization was explored using a reduced external Mg2(+) model. Single and dual whole cell patch-clamp recordings were performed in hippocampal cultures in three concentrations of external Mg2(+). In decreased Mg2(+) medium, the individual cells transitioned to spontaneous bursting behavior. In lowered Mg2(+) media the larger excitatory synaptic events were observed more frequently and fewer transmission failures occurred, suggesting strengthened synaptic transmission. The event synchronization was calculated for the neural action potentials of the cell pairs, and it increased in media where Mg2(+) concentration was lowered. Analysis of surrogate data where bursting was present, but no direct or indirect connections existed between the neurons, showed minimal action potential synchronization. This suggests the synchronization of action potentials is a product of the strengthening synaptic connections within neuronal networks.