‘Synaptic Vesicles’ in the Neurohypophysis

Abstract

ELECTRON microscope studies of the neurohypophysis have shown that the terminal branches of the hypothalamo-hypophysial tract fibres contain, in addition to mitochondria, vesicles or granules of two kinds distinguished by their size^1,2. The larger inclusions each have a diameter of the order of 100–300 mµ, (1000–3000 Å.), and are thought to represent the secretory material which may be demonstrated by histochemical means, using the light microscope. The smaller inclusions, with diameters of approximately 30 mµ (300 Å.), have been described as synaptic vesicles¹ because they resemble in size inclusions found elsewhere in the nervous system at nerve terminals.