Brain Tissue Oxygen: In Vivo Monitoring with Carbon Paste Electrodes

In this communication we review selected experiments involving the use of carbon paste electrodes (CPEs) to monitor and measure brain tissue O(2) levels in awake freely-moving animals. Simultaneous measurements of rCBF were performed using the H(2) clearance technique. Voltammetric techniques used include both differential pulse (O(2)) and constant potential amperometry (rCBF). Mild hypoxia and hyperoxia produced rapid changes (decrease and increase respectively) in the in vivo O(2) signal. Neuronal activation (tail pinch and stimulated grooming) produced similar increases in both O(2)and rCBF indicating that CPE O(2)currents provide an index of increases in rCBF when such increases exceed O(2) utilization. Saline injection produced a transient increase in the O(2) signal while chloral hydrate produced slower more long-lasting changes that accompanied the behavioral changes associated with anaesthesia. Acetazolamide increased O(2) levels through an increase in rCBF.