SUBCELLULAR DISTRIBUTION OF BIOGENIC MONOAMINES IN THE CENTRAL NERVOUS SYSTEM OF <i>ANODONTA CYGNEA</i> L. AS REVEALED BY DENSITY GRADIENT CENTRIFUGATION

Abstract

Abstract— Differential and gradient centrifugation revealed that 90 per cent of the 5‐HT, dopamine and noradrenaline in the CNS of the fresh water mussel was bound to particles; 60‐70 per cent of the bound monoamines appeared in the mitochondrial and 15‐20 per cent in the microsomal fraction. Spectrofluorimetric assay and electron microscopic analysis of the subfractions obtained by separation of the mitochondrial fraction on sucrose density gradients showed that the nerve endings and their dense‐core vesicles were concentrated in fractions with high relative specific activity of the three monoamines. This supports the proposed function of these monoamines as interneuronal mediators. Osmotic shock treatment resulted in the formation of a synaptosomal subfraction of low density displaying a high relative specific activity for 5‐HT. From the results obtained one cannot draw clear‐cut conclusions regarding the participation of subcellular particles in the storage of serotonin detectable in the perikarya by means of histochemical methods.