Wireless voltammetry recording in unanesthetised behaving rats

In vivo voltammetry is a valuable technique for rapid measurement of dopamine in the brain of freely behaving rats. Using a conventional voltammetry system, however, behavioural freedom is restricted by cables connecting the head assembly to the measurement system. To overcome these difficulties, we developed a wireless voltammetry system utilizing radio waves. This system consisted of a potentiostat and transmitter system that was mounted on the back of the rat, and a receiver and analysis system. A single-step pulse (100-250 mV) was applied at 4 Hz after an activation pulse to a carbon fibre recording electrode (diameter: 7 μm). Measurement of dopamine (detection limit: 2.7 × 10−7 M) was demonstrated in vitro. In vivo experiment was performed at least 1 week after the recording electrode was implanted in the rat striatum. Administration of 2-phenylethylamine to rats increased dopamine signal current, which was consistent with the result in the microdialysis measurement. During a resident-intruder test, dopamine signal current in a resident rat increased upon introduction of an intruder rat. These results show that the present wireless system is useful for a long-term measurement of dopamine in behaving rats.