Huntington's Disease Research Today is a free monthly online journal that collates and summarizes the latest research about Huntington's Disease, including details on genetics, causes, symptoms, treatment. | ||||||||
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Firing rates of pallidal neurons are similar in Huntington's and Parkinson's disease patients.Tang JK, Moro E, Lozano AM, Lang AE, Hutchison WD, Mahant N, Dostrovsky JO Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8. According to the now classical basal ganglia-thalamocortical circuitry model, the chorea of Huntington's disease (HD) and the hypokinesia in Parkinson's disease (PD) are explained by a decrease in the inhibitory output (reduced firing rates) from the globus pallidus internus (GPi) in HD and increased output in PD. Differences between firing patterns might also be a factor contributing to the different symptoms, however. To test the predictions of the model we examined neuronal firing rates and patterns in two HD patients and 14 PD patients. Single-cell, microelectrode recordings were obtained from awake patients undergoing stereotactic surgery for implantation of deep brain stimulating (DBS) electrodes in the GPi. The mean neuronal firing rate in the GPi of HD patients was 81.8+/-4.3 Hz (mean+/-SEM), which was not significantly different from that in PD patients (89.9+/-3.0 Hz). Firing pattern analyses using measurements of burst index, coefficient of variation, and percentage participation of spikes in bursts revealed, however, that GPi neurons in HD patients fired in a more regular pattern (fewer "bursts") than in PD patients. These results suggest that the rate-based model does not adequately explain the motor abnormalities present in the two HD patients studied. Furthermore, the findings did reveal a difference between firing patterns in the HD and PD groups, thereby supporting the role of altered firing patterns in the pathophysiology of these diseases. Published 27 September 2005 in Exp Brain Res, 166(2): 230-6.
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