Using carbon fibre microelectrodes to monitor the oxidative metabolism of blowfly eyes

Abstract

The oxidative metabolism in animal tissues can be conveniently monitored by measuring tissue PO2 with a carbon fibre microelectrode. We have established a recording configuration in a living animal by insertion of a carbon fibre electrode (CFE) into the retina of a blowfly (Calliphora vicina – chalky). The current flowing over an exposed carbon disc at the tip of an insulated carbon fibre with 5 µm diameter is linearly proportional to PO2 when the PO2 was varied between 0 kPa (100% N2) and 100 kPa (100% O2) in the recording chamber. The slight changes in sensitivity of CFE during the recording time were corrected by calibrationsperformed at the start and at the end of the experiments. Exposure of the eye to bright light caused a drop in tissue PO2. Hypoxia increased with the stimulation time, reaching a maximum after about 20 s (∆PO2=11.6 kPa). These results are in good agreement with direct measurements of O2 consumption in isolated eyes.