The uptake of tryptophan and tyrosine by the brain has been studied in 6 manic-depressive patients and in 8 schizophrenics. In an attempt to saturate the blood-brain transport mechanisms, this uptake has been evaluated by measuring the arteriovenous differences (arterial plasma-internal jugular plasma) of these two amino acids before and after perfusion with Z,-dopa and L-5-HTP. Considering a positive difference as an uptake and a negative one as an outflow, results show (1) in melancholia an uptake of tryptophan and an outflow of tyrosine; (2) in mania an uptake of tyrosine and an outflow of tryptophan, and (3) in schizophrenia an outflow of tryptophan accompanied with either an uptake or an outflow of tyrosine. In addition, the kinetics of tryptophan binding to plasma proteins and the ratio of tryptophan/tyrosine uptake are different in manic-depressive illness and in schizophrenia. These results support the view that a disturbance in the blood-brain transport mechanisms of tryptophan and tyrosine could be involved in the physiopathology of manic-depressive illness and schizophrenia.
Fluorescence microscopy of rat brains after administration of (+)-erythro-DOPS has been studied. (+)-erythro-DOPS induced an increase of brain NE part of which was formed in the capillary walls. The slight diminution of this increase when (+)-erythro-DOPS was administered after inhibition of peripheral decarboxylase, might result from the algebraic sum of two inversely acting processes: suppression of NE synthesis in the capillary walls and enhancement of parenchymatous NE in some brain areas. (+)-erythro-DOPS enters different brain structures non specifically and NE is formed in DA and 5-HT systems, displacing the amines especially at the terminals; the NE formed by (+)-erythro-DOPS in NE systems should be rapidly catabolised. Possible pharmacological effects of (+)-erythro-DOPS administration involve consideration of the lack of topical specificity of NE formation; the displacement of 5-HT and DA; and the fact (+)-erythro-DOPS produces (+)-NE, and not naturally occurring NE.
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