Effects of L‐dopa on the H‐reflex in Parkinsonism*

A bstract : The monosynaptic reflex (H‐reflex) was studied in 47 parkinsonian patients, before and after the oral administration of L‐dopa. In the group clinically benefited by L‐dopa (characterized before treatment by bradykinesia and rigidity), initially there was a markedly short onset time for the H‐reflex recovery curve. L‐dopa significantly reduced the bradykinesia and rigidity, and the onset time for the H‐reflex recovery curve increased. These findings indicate that the previously facilitated total excitation level of the anterior motoneuron pool was suppressed by L‐dopa. Patients who had moderate to moderately severe bradykinesia and rigidity, and a short onset time for the H‐reflex recovery curve, were better candidates for L‐dopa therapy.