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Decrease in presynaptic inhibition on heteronymous monosynaptic Ia terminals in patients with Parkinson's disease
1The Third Department of Internal Medicine, Shinshu University School of Medicine, Matsumoto, Japan.
Purpose:
Heteronymous Ia facilitation from the quadriceps to the soleus was studied to clarify central motor control through presynaptic inhibition (PSI) on Ia terminals of spinal motoneurons in Parkinson's disease.
Methods:
17 patients with Parkinson's disease and 36 control subjects participated in the study. Because the early part of facilitation reflects the degree of PSI, the extent of facilitation was quantified as the slope, within 0.8 msec of onset.
Results:
Heteronymous Ia facilitation in the patients was greater than in the age-matched control participants. PSI was negatively correlated with the walking speed of the patients. In the patients examined twice, lessening of bradykinesia was correlated to a decrease in PSI but not lessening of rigidity.
Conclusion:
These findings indicate that the degree of PSI is decreased and disturbance of the central control of PSI may relate to gait disturbance in Parkinson's disease.