ISSN:
1432-0878
Keywords:
Tegmental reticular nucleus (Bechterew)
;
Serotonin neurons
;
Reticular formation
;
Ultrastructure
;
Synaptic organization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The organization of the tegmental reticular nucleus of von Bechterew (TRN) has been analyzed in Nissl and Golgi material, by fluorescence histochemistry, and by electron microscopy. In the albino rat, the TRN situated in the ventral paramedian midbrain and pontine reticular formation, contains two principal types of neurons. The first is a population of large multipolar neurons (40–80 μm diameter) with abundant Nissl substance and 4–7 smooth dendrites which may extend up to 500 μm in length. The second is medium-sized fusiform neurons (14–40 μm diameter) with less Nissl substance and two primary dendrites that originate from each pole of the soma and have a more closely ramifying dendritic field. Fluorescence histochemistry demonstrates that serotonin neurons constitute one component of the medium-sized neuron group. A third neuronal type, infrequently encountered at the outer margins of the nucleus, corresponds to the large, multipolar isodendritic neurons (soma diameter 40–80 μm) of the pontine reticular formation. Ultrastructural analysis of the TRN also demonstrates large and medium sized neurons which are present, together with numerous large dendritic trunks, between bundles of myelinated axons traversing the TRN in both rostrocaudal and transverse planes. This distinctive arrangement produces the appearance of “gray islands” between myelinated axon bundles. Within these areas, abundant synaptic terminals occupy a large proportion of the available terminal space on the surface of dendrites and perikarya, particularly of the large type of neuron. Two types of synaptic terminals are encountered; S-type synapses contain lucent spherical synaptic vesicles and F-type synapses contain flattened lucent vesicles. In addition there is a small number of synaptic terminals with scattered 100–120 nm diameter dense core vesicles in a population of smaller pleomorphic vesicles. These account for no more than 10% of the synaptic terminal population.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00236166
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