Changes in Concentration of Extracellular Aspartate and Glutamate During Cortical Spreading Depression in the Rat Cerebral Cortex

Song, Jun Hyeok; Park, Youn Kwan; Chung, Yong Gu; Chung, Heung Seob; Suh, Jung Keun; Lee, Ki Chan; Lee, Hoon Kap

Abstract

The author has examined the effect of cortical spreading depression(CSD) on the changes in extracellular concetration of aspartate and glutamate in the neocortex of anesthetized rats using microdialysis and high performance liquid chromatography(HPLC). The rats were prepared by halothane anesthesia and artificial ventilation. Rats were placed in a stereotaxic frame, and craniotomies were performed over the frontal and parietal cortexes on one side. The CSD was elicited by local application of KCI-soaked small pellets to the frontal cortex. The CSD was monitored by the changes of direct current(DC) potential in the parietal cortex. The microdialysis probe was implanted in the anterior part of the parietal cortex. Amino acids were analyzed by HPLC and fluorescence detection. Baseline concentration of the aspartate was 34.9+/-15.9nM and that of glutamate was 189.8+/-29.1nM(mean standard deviation). The perfusate for analysis was obtained 30 minutes after the beginning of the 300mM KCl induced CSD. Aspartate was found to increase to 146+/-55% baseline, glutamate up to 173+/-30% baseline(mean standard deviation). The increment of glutamate was statistically significant(p<0.05). Then 2M KCI-doaked pellets were applied for more frequent CSD amd the samples were collected. Aspartate increased up to 258+/-97% baseline, glutamate up to 174+/-57% baseline(mean standard deviation), The increment of glutamate and aspartate accompanying 2M KCI induced CSD were also statistically significant(p<0.05). These data suggest that the excitatory amino acids were released during the CSD and this may explain the various aspects of CSD that could contribute to the secondary neuronal damage in the compromised nerve cell.