A reliable multichannel commutator for making electrical contact with conscious, freely moving rats

A counterbalanced mercury swivel arrangement is often used to make connections between electrodes implanted in the brain of conscious laboratory animals and electronic equipment so that movement is not restricted. There are certain disadvantages associated with this system and an alternative is described which is based on a rhodium plated slip ring. The device is reliable, robust, causes minimal hindrance to the movement of the animal and causes virtually no interference noise to low level electrical signals. The slip ring based commutator has been incorporated into an automated system for making in vivo voltammetric recordings from conscious rats where currents of less than 100 nA are measured. Some of the results are shown.