Optical monitoring of PO 2 changes and simultaneous recording of bioelectric activity in human and animal brain slices

Abstract

For investigations of hypoxic effects in nervous tissue, brain slices are often used as a model system. This provides the advantage that parameters of the micromilieu, e.g. pH and temperature can easily be controlled and measurements of different data, e.g. bioelectric potentials, ion activities etc. can be performed. It is of special importance that the PO 2 the slice preparation is exposed to is equally controlled under these conditions. Therefore, a PO 2 monitoring system is needed which provides representative values for the tissue environment. This requirement is fulfilled by an optical PO 2 sensing method based on phosphorescence quenching as a function of PO 2. Here, the application of this method as adapted for use in in vitro models is described and compared to the polarographic oxygen-sensing method. Both the optical and polarographic methods are comparable regarding accuracy and response time of measurements. Furthermore, both the optical method and electrophysiological measurements can be combined. Lastly, under experimental conditions, neither the phosphorescent dye Palladium-meso-tetra-4-carboxyphenyl-porphine nor the illumination necessary for excitation of the dye influence bioelectric activity of neuronal tissue in vitro. In conclusion, the optical PO 2 sensing method presented here provides a tool for reliable and continuous monitoring of PO 2 in the immediate environment of brain slice preparations.