Internal Pallidal Neuronal Activity During Mild Drug-Related Dyskinesias in Parkinson's Disease: Decreased Firing Rates and Altered Firing Patterns

Abstract

The neuronal basis of hyperkinetic movement disorders has long been unclear. We now test the hypothesis that changes in the firing pattern of neurons in the globus pallidus internus (GPi) are related to dyskinesias induced by low doses of apomorphine in patients with advanced Parkinson's disease (PD). During pallidotomy for advanced PD, the activity of single neurons was studied both before and after administration of apomorphine at doses just adequate to induce dyskinesias (21 neurons, 17 patients). After the apomorphine injection, these spike trains demonstrated an initial fall in firing from baseline. In nine neurons, the onset of on was simultaneous with that of dyskinesias. In these spike trains, the initial fall in firing rate preceded and was larger than the fall at the onset of on with dyskinesias. Among the three neurons in which the onset of on occurred before that of dyskinesias, the firing rate did not change at the time of onset of dyskinesias. After injection of apomorphine, dyskinesias during on with dyskinesias often fluctuated between transient periods with dyskinesias and those without. Average firing rates were not different between these two types of transient periods. Transient periods with dyskinesias were characterized by interspike interval (ISI) independence, stationary spike trains, and higher variability of ISIs. A small but significant group of neurons demonstrated recurring ISI patterns during transient periods of on with dyskinesias. These results suggest that mild dyskinesias resulting from low doses of apomorphine are related to both low GPi neuronal firing rates and altered firing patterns.

Human Central Nervous System Circuits Examined in Patients with Parkinson's Disease Using the Electrodes Implanted for Deep Brain Stimulation

“…Alonso-Frech et al (2006) found basically the same results and suggested that the increase in the power of the 4-10 Hz frequency band could account for dopamineinduced dyskinesias in PD patients. This has been also pointed out more recently by Lee et al (2007) who observed that a decrease in neuronal firing rate in the GPi preceded the onset of dyskinesias induced by the administration of apomorphine. Kuhn et al (2006b) calculated in 9 PD patients the STN LFP power over the frequencies of the most prominent spectral peak within the 8-35 Hz frequency band and of any peak in the 60-90 Hz band.…”

Dynamics of firing patterns, synchronization and resonances in neuronal electrical activities: experiments and analysis

“…This implied that the irregular firing pattern might be stochastic. The irregular firing patterns of neurons in the globus pallidus internus (GPi) were related to dyskinesias induced by low doses of apomorphine in patients with advanced PD [64]. After the apomorphine injection, the behavior of patients often fluctuated between transient periods being dyskinesias and those without dyskinesias.…”

Globus Pallidus Internus Deep Brain Stimulation as Rescue Therapy for Refractory Dyskinesias following Effective Subthalamic Nucleus Stimulation

“…Dyskinesias have been associated with reduced pallidal firing rates and altered firing patterns [26,27] as well as increased pallidal neuronal synchronisation at low frequencies (<10 Hz) [28,29,30,31]. The use of GPi stimulation for the treatment of dyskinesias is well supported by the literature [32,33,34,35], and it is likely that the success of this procedure is in part related to inhibition of aberrant neuronal activity at this nucleus [36,37,38].…”