smokingresponsive juvenileonset parkinsonism we describe a patient with juvenile levodoparesponsive parkinsonism who reported a dramatic response to cigarette smoking with transient but marked improvement of motor symptoms associated with oculogyric crises and psychotic behavior his betacit singlephoton emission computed tomography scan showed a complete absence of presynaptic dopaminergic nerve terminals effect of different psychoactive drugs on serum and brain tryptophan levels a considerable amount of evidence indicates that the brain tryptophan level depends on circulating tryptophan changes of tryptophan concentration have also been described to modify the activity of benzodiazepines and tricyclic antidepressants in the present study a series of psychoactive drugs have been preliminarily screened for their activity on brain and plasma tryptophan levels the results obtained suggest that tryptophan may be involved to varying extents in the activity of different psychoactive compounds