Microthalamotomy effect during deep brain stimulation: potential involvement of adenosine and glutamate efflux

Deep brain stimulation (DBS) of the thalamus is widely used in humans to treat essential tremor and tremor dominant Parkinson's disease. After DBS lead implantation, tremor is often reduced even without electrical stimulation. Often called "microthalamotomy" effect, the exact mechanism is unknown, although it is presumed to be due to micro lesioning. Here, we tested whether microthalamotomy effect may, in fact, be mediated via release of neurotransmitters adenosine and glutamate, using fast scan cyclic voltammetry (FSCV) and amperometry, respectively. Implantation of microelectrodes into the ventrolateral (VL) thalamus of the rat resulted in transient rise in adenosine and glutamate level from mechanical stimulation. Similarly, high frequency stimulation (100 - 130 Hz) of the VL thalamus also resulted in adenosine and glutamate release. These results suggest that glutamate and adenosine release may be an important and unappreciated mechanism whereby mechanical stimulation via electrode implantation procedure may achieve the microthalamotomy effect.