Ultrastructural data on the cytology and cytochemistry of the autonomic nervous system

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Abstract
Our demonstration deals with two topics: the first one concerns the so-called large granular vesicles (l.g.v.) or large dense-core vesicles in the nerve fibres and cells of the autonomic nervous system; the second one is related with the cytochemistry of noradrenaline in the sympathetic adrenergic neurons. All the reported observations were made on rat tissues. The l.g.v. measure 70 to 120 nm in diameter; the centre of such vesicles contains a more or less dense granule. This aspect is seen after fixation with osmium tetroxide as well as after fixation with glutaraldehyde or by a mixture of formaldehyde and glutaraldehyde, followed by osmium tetroxide. In the last case, the granule appears generally more electron-dense than after osmium tetroxide alone. The l.g.v. are widely distributed in the different types of fibres of the autonomic nervous system. They were first described in axon terminals of the preganglionic cholinergic fibres (Taxi 1961) and later they were observed in adrenergic peripheral nerve fibres, where they are associated with small granular vesicles (s.g.v.); these s.g.v. have a similar size to the classical agranular synaptic vesicles. No matter which fixative is used, the central granule of s.g.v. is always extremely dense. The two kinds of granular vesicles (l.g.v. versus s.g.v.) differ also in their behaviour under the action of reserpine (5 mg/kg i.p.). The dense granules of s.g.v. are depleted (Pellegrino de Iraldi & de Robertis 1961), whereas those of l.g.v. remain practically unaffected (figure 1), in both cholinergic and in adrenergic nerve fibres (Taxi 1965).

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