Application of Thallium Autometallography for Observation of Changes in Excitability of Rodent Brain following Acute Carbon Monoxide Intoxication

Abstract

Purpose: Thallium (TI+) autometallography is often used for the imaging of neuronal metabolic activity in the rodent brain under various pathophysiologic conditions. The purpose of this study was to apply a thallium autometallographic technique to observe changes in neuronal activity in the forebrain of rats following acute carbon monoxide (CO) intoxication. Methods: In order to induce acute CO intoxication, adult Sprague-Dawley rats were exposed to 1100 ppm of CO for 40 minutes, followed by 3000 ppm of CO for 20 minutes. Animals were sacrificed at 30 minutes and 5 days after induction of acute CO intoxication for thallium autometallography. Immunohistochemical staining and toluidine blue staining were performed to observe cellular damage in the forebrain following intoxication. Results: Acute CO intoxication resulted in significant reduction of TI+ uptake in major forebrain structures, including the cortex, hippocampus, thalamus, and striatum. In the cortex and hippocampal CA1 area, marked reduction of TI+ uptake was observed in the cell bodies and dendrites of pyramidal neurons at 30 minutes following acute CO intoxication. There was also strong uptake of TI+ in astrocytes in the hippocampal CA3 area following acute CO intoxication. However, there were no significant histological findings of cell death and no reduction of NeuN (+) neuronal populations in the cortex and hippocampus at 5 days after acute CO intoxication. Conclusion: The results of this study suggest that thallium autometallography can be a new and useful technique for imaging functional changes in neural activity of the forebrain structure following mild to moderate CO intoxication.