Measurement of synchronous activity by microelectrode arrays uncovers differential effects of sublethal and lethal glutamate concentrations on cortical neurons.

We grew cultures of rat cortical cells on microelectrode arrays to investigate the effects of glutamate-mediated neurotoxicity as a model of traumatic brain injury. Treatment with two different concentrations of glutamate, 175 and 250 μM, led to different outcomes. Cultures treated with 250 μM glutamate suffered a loss in overall activity that was not seen in cultures treated with 175 μM glutamate. An analysis of the changes in the synchronization of action potential firing between electrodes, however, revealed a loss of synchronization in subsets of electrode pairs treated with both the higher and lower concentrations of glutamate. We found that this loss of action potential synchronization was dependent on the initial amount of synchronization prior to injury. Finally, our data suggest that the synchronization of electrical activity as well as the susceptibility to loss of firing synchrony is independent of the distance between neurons in a network.