Portable microstimulator for chronic deep brain stimulation in freely moving rats

In the last decades, deep brain stimulation (DBS) has been widely used as a functional surgical strategy for the treatment of a variety of neurological and psychiatric disorders, including Parkinson's disease (PD), dystonia, epilepsy, depression or obsessive-compulsive disorder. While the therapeutic benefits of DBS are now recognized, experimental data on its mechanisms and impact at long term remain poor. This is mainly due to the lack of a microstimulation system adapted for chronic DBS in small laboratory animals. In this context, we have developed a microstimulator for DBS adapted to rat. This device, which has a size and weight compatible for use in freely moving rat, can be clipped to a support fixed on the animal's head. This easy "removal" property is crucial because it enables removing or even switching the microstimulator during the experiments without having to anaesthetize or to operate the animal, thus minimizing stress. The design of the microstimulator allows to set the DBS parameters easily (intensity, frequency and pulse width) and to replace the battery for long-term DBS. To validate our device, we performed continuous DBS of the subthalamic nucleus (known to improve motor deficits in clinic) in a classical rat model of PD during 5 weeks. We show that this long duration stimulation reduces significantly PD-induced akinesia without inducing animal discomfort and tissue damage. These first data demonstrated that long term DBS procedure in behaving rat is now workable.