Wireless in vivo voltammetric measurements of neurotransmitters in freely behaving rats.

An improved telemetric system based on either differential pulse voltammetry (DPV) or direct current amperometry (DCA) "diffused" via a single-way infrared (IR) transmission channel is introduced. The structural design of this system is very small and weighting only few grams but above all and unlike similar pre-existing instruments based on IR transmission, the present system works on a single-way communication, thus avoiding problems related to cross-talking between two-way channels that ends in altered functionality of the measuring electrode system. In addition, it is immune from electromagnetic interferences that disturb radio-frequency transmission. The system appeared already sensitive to both dopamine (DA) and serotonin (5-HT) using DCA and DPV either in vitro as well as in vivo. In particular, parallel in vivo experiments within anaesthetised rats prepared for classical wire-connected DCA or for wireless DCA resulted in superimposing data when the 5-HT system in the frontal cortex of anaesthetised rats was challenged with fluoxetine. In the present study, we have further refined and then successfully extended the wireless methodology to conscious freely moving rats and further verified the chemical nature of the DA and 5-HT current related signals recorded with wireless DCA in prefrontal cortex using Nafion coated micro-biosensors via dedicated pharmacological treatments.