Morphological studies on the distribution and properties of the granulated vesicles in the brain.

Abstract

The distribution and fine structure of the granulated vesicles in the central nervous system of rodents (rats, guinea pigs and rabbits) have been investigated by means of electron microscopy. Some properties of these vesicles were studied by the administration of certain drugs, radioautography and cytochemistry at the fine structural levels.1. Granulated vesicles were most numerous in the nuclei hypothalamicus anterior, paraventricularis and ventro-medialis and less numerous in the subependymal layer of the third or fourth ventricles and the nuclei hypothalamicus lateralis and posterior. A moderate number of granulated vesicles were demonstrated in the preoptic areas, the central gray matter of the midbrain, the nucleus interpeduncularis, the mamillary body, formatio reticularis (midbrain and pons), locus caeruleus, nucleus habenulae, nucleus dorsalis nervi vagi, area postrema and supraoptic crest.2. The midbrain and pontine reticular formation showed many axo-somatic synapses, and some presynaptic bags of granulated vesicles were seen mixed with synaptic vesicles. In the perikaryon of the nerve cells of the formatio reticularis, area postrema and nucleus hypothalamicus posterior, mature and various immature types of granulated vesicles were concentrated around the Golgi apparatus and in the neighbourhood of the multivesicular bodies.3. The membrane (80A) of granulated vesicles showed a trilaminar structure and the dense core inside consisted of electron-opaque subunits of about 40A in diameter and sometimes showed clear globular structures.4. Intraperitoneal injection of reserpine (10mg/kg) caused the majority of granulated vesicles in the madial hypothalamus to evaculate their core or their core to decrease in electron density and to lose catecholamine. An injection of Win 18501-2 resulted in a decrease in the content of noradrenalin and a parallel decrease in the number of granulated vesicles in the hypothalamus. The dopamine content did not show any relation with the morphological alteration of granulated vesicles in animals injected with Win 18501-2.5. The distribution of acetylcholine-esterase activity was studied by electron microscopy by the method of KARNOVSKY. In the neuropil of the nucleus caudatus and in the mossy fiber endings of the cerebellum, activity was demonstrated on the plasma membranes of the preterminal axons, presynaptic terminals and dendritic branches. The locus caeruleus, nucleus dorsalis nervi vagi and medial hypothalamus also showed activity on the plasma membrane of the axon terminals which contained both granulated and synaptic vesicles.6. At various times after intraperitoneal administration of H3-DOPA to the rat pretreated with catron, the brain was fixed as described in methods 1 (normal distribution of the granulated vesicles) and the ultrathin sections were coated with Sakura NA-Hl by the wire-loop or pushing method. Electron microscopic autoradiography of the nuclei hypothalamicus anterior and ventro-medialis showed that two-thirds or three-quarters of the total silver grains were located on the neuropils. In the neuropils about 70% of the silver grains were localized on the synaptic endings and dendrites. There was a tendency for the number of silver grains on the presynaptic terminals containing granulated vesicles to increase with time after the administration of H3-DOPA.