| Research Abstract |
Serotonin antiserum was obtained by immunization of rabbits with serotonin coupled with bovine thyroglobulin by the mannich reaction. Using the immunohistochemical technique, maps of the distribution of serotonin neurons were made for the CNS of various mammals and other vertebrate classes. The total numbers of serotonin neurons in the brain were about 25,000 in mice, 50,000 in rat, and 135,000 in monkey. Most of these neurons in the brainstem occupy large parts of the raphe nuclei. The axonal processes of serotonin neurons continue to long branched fibers that are complicated and widely spread. All fibers contain many small, spherical varicosities. Except for thick myelinated tracts, serotonin fibers are distributed in all areas of the CNS. In the visual cortex of Macaca fuscata, the overall density of varicose fibers is about 770,000/mm^3 and the concentration of immunoreactive varicosities (ca 1,400,000/mm^3) is highest in the layer IVc. Serotonin fivers are to be found in the ventricular lumen and the subarachnoid space.
Processes of serotonin neurons form a wide-spread network by the repetition of ramifications and reunions. Such three-dimensional networks are formed in almost all regions of gray matter. The serotonin neuron system does not correspond to a certain nervous circuit to connect centers for special functions. These neurons are related to other neurons through en passant type synapses, and may exert their effect on those neurons en masse.
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