Human microdyalisis during acute high frequency stimulation of internus globus pallidus increases dopamine release and improves parkinsonian symptoms

Abstract

Background: Despite of clinical efficacy of high frequency stimulation in Parkinson's disease has been well established, its interaction with neurotransmitter release is still unknown. Methods: In five patients, a microelectrode was inserted together with microdialysis probe (2mm apart) and the stimulating contact of microelectrode and the dialysis membrane (3 mm) were in the same dorso-ventral level in the GPi. After the insertion of the probe, samples were collected every 10 minutes for 70 min. First three samples corresponded to baseline levels of dopamine, followed by another 10 minute-stimulation-sample and the three remaining post-stimulation-sample. Results: Our results showed that during the stimulation period, patients 1, 2, 3 and 4 showed a huge increase in dopamine levels while patient 5 had a small increase (Chi-square(1,6) = 15,09; p = 0,020). Another interesting data is that after the stimulation period (PS samples), there was another increase in dopamine levels observed in patients 1, 2 and 5. Additionally, during intraoperative physiologic testing, all patients exhibited suppression of their parkinsonian symptoms with electrical stimulation of the globus pallidus. The stimulation applied through GPi showed an improvement of contralateral lower and upper limb akinesia. Conclusions: The present study provides an interesting information to understand how high frequency stimulation can be an efficient treatment for advanced Parkinson's patients.