The objective of this proposal is to study binding proteins for monoamine neutrotransmitters that have been detected in synaptosome cytoplasm and that are involved in storage and translocation of monoamines. The existence of such amine binding sites has been suggested from physiological, pharmacological, and morphological studies. Emphasis is placed on the serotonin binding protein as a model. The protein will be purified by chromatography on affinity columns and on molecular sieves (ultrogel AcA 22) and by preparative gel electrophoresis. The mechanism of enhancement of the binding by Fe ions will be further studied by electron spin resonance (EPR) measurements. The mechanism of the inhibitory effect of reserpine, CZ-74 and vinblastine will be studied. The serotin binding protein in brain will be compared to the proteins of platelets with similar electrophoretic mobility. Using the myenteric plexus as a source of serotonergic neurons rich in serotonin binding protein, experiments are designed to purify the binding protein and raise antibodies against it. Questions concerning the interaction of other biogenic amines with serotonin expressed through their effect on serotonin binding protein are also to be considered. In this regard, experiments are proposed in which specific inhibitors of biosynthesis of catecholamines will be used to depress catecholamine concentrations. In addition both electrolytic lesions and chemical lesions will be induced in major dopaminergic cell bodies (substantia nigra) or major noradrenergic cell bodies (locus coeruleus) to cause degeneration of the respective axonal tracts. Chemical lesions will be induced by intracerebral administration of appropriate neurotoxins: 6-hydroxydopamine or 6-hydroxydopa. Serotonin binding capacity of lesioned animals will be tested in areas enriched in nerve endings (neostriatum and cortex). The studies will attempt to further define interaction between neuronal pathways utilizing different neurotransmitters. Such interactions may be inferred from many different observations, and suggest concerted action in the regulation of different neurotransmitter concentrations.