Electrochemical calibration of in vivo brain dialysis samplers

Measurement of state-related changes in the concentration of an endogenous substance using the in vivo dialysis technique requires a definition of the factors which relate the concentration detected in the outflowing perfusate to the concentration actually occurring in the extracellular space in which the sampler is located. In determine these factors, a rapid and highly accurate detector system is required which measures the concentration recovery in the perfusate and the dead space of the entire sampling system. To reduce the limitations of the microdialysis technique, two electrochemical microcells were developed for calibration of dialysis probes by computerized voltammetry. The electrochemically calibrated samplers were implanted into freely moving cats to measure concentration changes of monoamine metabolites in synchrony with sleep stages identified by polygraphy in order to demonstrate the applicability of electrochemical calibration in dialysis methods used in behavioral investigations.