Deep brain stimulation by optimized stimulators in a phenotypic model of dystonia: Effects of different frequencies.

Deep brain stimulation (DBS) of the globus pallidus internus (GPi, entopeduncular nucleus, EPN, in rodents) has become important for the treatment of generalized dystonia, a severe and often intractable movement disorder. It is unclear if lower frequencies of GPi-DBS or stimulations of the subthalamic nucleus (STN) are of advantage. In the present study, the main objective was to examined the effects of bilateral EPN-DBS at different frequencies (130 Hz, 40 Hz, 15 Hz) on the severity of dystonia in the dtsz mutant hamster. In addition, STN stimulations were done at a frequency, proven to be effective by the present EPN-DBS in dystonic hamsters. In order to obtain precise bilateral electrical stimuli with magnitude of 50 µA, a pulse width of 60 µs and defined frequencies, it was necessary to develop a new optimized stimulator prior to the experiments. Since the individual highest severity of dystonic episodes is known to be reached within three hours after induction in dtsz hamsters, the duration of DBS was 180 min. During DBS with 130 Hz the severity of dystonia was significantly lower within the third hour than without DBS in the same animals (p < 0.05). DBS with 40 Hz tended to exert antidystonic effects after three hours, while 15 Hz stimulations of the EPN and 130 Hz stimulations of the STN failed to show any effects on the severity. DBS of the EPN at 130 Hz was most effective against generalized dystonia in the dtsz mutant. The response to EPN-DBS confirms that the dtsz mutant is suitable to further investigate the effects of long-term DBS on severity of dystonia and neuronal network activities, important to give insights into the mechanisms of DBS.