THE FINE-STRUCTURE OF LARGE DENSE-CORE ORGANELLES IN HUMAN LOCUS-COERULEUS NEURONS

Protein bodies, the characteristic spherical organelles present in hum an monoamine neurons, have been shown in previous electron microscope studies to originate as dense bodies in mitochondria. This study was d esigned to investigate the presence of catecholamine reaction products in the dense bodies of locus coeruleus neurons, in frozen fresh post- mortem brain tissue with the use of potassium permanganate (KMnO4) fix ation. This fixation procedure forms a dense KMnO4/catecholamine react ion product, visible in the electron microscope, in the large dense-co re vesicles of experimental animals. Our results demonstrate the local ization of KMnO4 dense product in the cores of double membrane-bound s pherical organelles, as well as in spherical structures in the matrix of typical mitochondria. No typical large dense-core vesicles were obs erved in these catecholamine neurons of the tissues studied. Our findi ngs are consistent with the notion that altered mitochondria may contr ibute to the formation of a new type of large dense-core vesicle in th e locus coeruleus neurons of man, which is probably an evolutionary ad aptation of amine-storing organelles.