The Effect of L-3, 4-dihydroxyphenylalanine and Dl-5-hydroxytryptophan on Rigidity and Tremor Induced by Reserpine, Chlorpromazine and Phenoxybenzamine.

A syndrome of akinesia, rigidity and tremor can be induced in rats after administration of reserpinel' 2 . A technique giving access to the activity of single efferent axons and motor units without interfering with the induced motor phenomena was developed for an analysis of the muscle control in the reserpine syndrome2 . A decrease of y -fibre activity and an increase of a-fibre activity was demonstrated simultaneously with the appearance of the motor phenomena after reserpine injection . The result showed that the a-moto-neurone hyperactivity of reserpine rigidity is not secondary to a hyperactivity of y -motor axons, These motor fibres serve as regulators of muscle spindle sensitivity and influence the a-moto neurones via the stretch reflex . The spontaneous muscle contraction maintaining the flexion posture of the rigid animal was shown to be due to a tonic activity of slowly contracting motor units2. Using the same technique we have extended the analysis to the motor disturbances caused by chlorpromazine and phenoxybenzamine and further studied the action of L-3, 4-dihydroxyphenylalanine (L-DOPA), DL-5-hydroxytryptophan (5-HTP), dopamine and 5-hydroxytryptamine (5-HT) on the drug induced condition. The distribution of the monoamines in the brain seems to be