[Electron microscopic analysis of the adrenergic nerve endings of the caudal mesenteric ganglion in cats].

The ultrastructure of nerve terminals in the cat inferior mesenteric ganglion was studied under fixation with 4% LiMnO4 solution according to the Richardson method modified by Hökfelt et al. This type of fixation is shown to be suitable in demonstrating, along with cholinergic terminals, numerous adrenergic endings. Four types of adrenergic organelles are revealed in the ganglion neurons; small and large granular vesicles 30-50 and 70-90 nm in diameter, respectively, tubular reticulum with electron-dense contents, and very small granular vesicles 15-20 nm in diameter. The localization of the adrenergic terminals and their relationships with other processes and cells of the inferior mesenteric ganglion are examined in detail. The origin and physiological role of the adrenergic nerve terminals in the ganglion are discussed.