The common pathophysiology of monaminergic psychoses: a new hypothesis

Several recent data indicate the blood-brain transport of amino acids as a critical factor in the synthesis of monoamines. The complex, peripheral and central regulation of TP transport plays an essential role sine TP-hydroxylase is not a saturated enzyme. The hydroxylated derivatives 5-HTP and dopa are probably transported into the brain by similar mechanisms as their precursors TP and tyrosine, respectively. The maic-depressive patients show an increased uptake of administered L-5-HTP in the depressive phase, whereas L-dopa uptake is enhanced in the manic phase. Heuristically, we propose a biochemical model of manic-depressive psychosis in which an increased TP uptake causes alternation in the balance of monoaminergic system activity. Depression is possibly characterized by a hyperserotonergic and a relative hypocatecholaminergic activity. In contrast, mania is possibly determined by a hypercatecholaminergic (NA and DA) and a relative hyposerotonergic activity. The data offered by the physiology of monoamines, the semeiology and the biological alterations of the manic-depressive psychosis, as well as the monoaminergic and the electrolyte theory of manic-depressive psychosis. A diminution of the transport of TP with consequent increase of that of tyrosine represents a possible biochemical model of schizophrenia which may be well explained by a hyposerotonergic-hyperdopaminergic activity, with or without noradrenergic insufficiency. This model is compatible with our knowledge on the monoamine physiology, the biological alterations of schizophrenia, the therapeutical results as well as with the classical clinical notions (typology, intermediate syndromes and crossed heritance).