Short communicationElectrochemical detection of endogenous glutamate release from rat spinal cord organotypic slices as a real-time method to monitor excitotoxicity

Excessive release of glutamate is believed to be a major component of cell damage following excitotoxicity associated with acute spinal cord injury. Using an in vitro model of excitotoxicity evoked by kainate on rat organotypic spinal slice cultures, we investigated the timecourse and extent of endogenous glutamate release following 1 h application of kainate using a commercially available biosensor placed on the ventral horn area of such slices. The release of glutamate peaked 7 min from the start of kainate (0.5 mM) application and then slowly declined to baseline prior to kainate washout. A lower concentration of kainate (0.1 mM) induced a smaller release that developed more slowly. At the end of each experiment, the number of pyknotic nuclei was counted to quantify cell death that was found to be about 10% of the total population with no significant neuronal loss. This finding accords with previous studies showing that, on the basis of neuronal counts at various times after kainate application, neuronal death was delayed. The present data demonstrate that a glutamate biosensor can be employed for real-time monitoring of endogenous glutamate release from an in vitro model of acute spinal cord injury applied to organotypic slices. This method can, therefore, be useful to study the cellular action of neuroprotective drugs targeting glutamate release mechanisms.