Distribution of Noradrenaline Storing Particles in Peripheral Adrenergic Neurons as Revealed by Electron Microscopy

Abstract

Abstract The cell bodies, the axons and the terminal parts of peripheral sympathetic neurons originating in the superior cervical ganglion and terminating in the dilator muscle of the iris were investigated in the rat by electron microscopy using potassium permanganate as a fixative. In all parts of the neuron granular vesicles were found. They were most numerous in the axonal enlargements of the nerve terminals, although also high numbers were found in some cell bodies, mostly localized in clusters in the peripheral parts of the cytoplasm. Two types of granular vesicles were found with a mean diameter of 495 Å (small) and 967 Å (large), respectively. The small granular vesicles were in majority, constituting about 98 per cent in the axonal enlargements in the dilator muscle of the iris. The number of vesicles in the axonal enlargements varied widely from 45 to 852 per enlargement. In all probability the small granular vesicles are the main storage site of noradrenaline in the peripheral adrenergic neurons. However, also the large ones probably contain an amine or at least are involved in the amine metabolism.