Reciprocal continuous inhibition in rigidity of Parkinsonism

A reciprocal continuous inhibition by flexor on extensor muscles was proved during Parkinsonian rigidity. Extensor motoneurone excitability was tested by Hoffmann's reflex and flexor activity was altered by lidocaine anaesthesia of the peroneal nerve (PN). During PN anaesthetic block, a gradual increase of Hoffmann's reflex was noted. It was statistically significant at the 15th minute after lidocaine injection, and was maximum at the 30th minute. The reciprocal inhibition was considerable in 16 patients with Parkinsonism, as recorded before treatment. In normal subjects, it was small and non-significant. After one month's treatment with L-dopa at the usual therapeutic dose, this reciprocal inhibition greatly decreased in the same patients. The origin of this reciprocal continuous inhibition is discussed.