Brain Tissue Oxygen: In Vivo Monitoring with Carbon Paste Electrodes

Abstract: In this communication we review selected experiments involving the use ofcarbon paste electrodes (CPEs) to monitor and measure brain tissue O₂ levels in awakefreely-moving animals. Simultaneous measurements of rCBF were performed using the H₂clearance technique. Voltammetric techniques used include both differential pulse (O₂) andconstant potential amperometry (rCBF). Mild hypoxia and hyperoxia produced rapidchanges (decrease and increase respectively) in the in vivo O₂ signal. Neuronal activation(tail pinch and stimulated grooming) produced similar increases in both O₂ and rCBFindicating that CPE O₂ currents provide an index of increases in rCBF when such increasesexceed O₂ utilization. Saline injection produced a transient increase in the O₂ signal whilechloral hydrate produced slower more long-lasting changes that accompanied the behavioralchanges associated with anaesthesia. Acetazolamide increased O₂ levels through an increasein rCBF.