Radiofrequency current density imaging of kainate-evoked depolarization

The purpose of this study was to examine whether radiofrequency current density imaging (RF-CDI) can quantitatively monitor depolarizations evoked by excitatory amino acids in a rat's brain. To evoke depolarization, a glutamate receptor agonist, kainate, was administered into the right lateral ventricle. First, electroencephalographic activity was recorded in a basal condition and after the application of kainate. Complex behavioral patterns were observed. Second, impedance measurements were performed to assess the change in conductivity of the brain due to kainate at the Larmor frequency of the imager. Calculated changes were about 17%. Third, a set of current density images was obtained with RF-CDI before and after the administration of kainate. Kainate-induced excitatory changes were observed on current density images as brighter regions, mainly in the hippocampal area compared with the same area in the basal condition.