SEROTONIN NEURONS IN NUCLEUS RAPHE MAGNUS OF THE RAT: A LIGHT AND ELECTRON MICROSCOPE IMMUNOCYTOCHEMICAL STUDY / 解剖学报

ABSTRACT

Serotonin (5-HT) neurons in the nucleus raphe magnus (NRM) of the rat were identified by light and electron microscope immunocytochemistry methods. Serotoninlike immunoreactive (5-HT-li) neurous were large multipolar and fusiform cells which mainly located in the ventrocaudal part of the NRM. With electron microscopic immunocytochemistry the following findings were revealed 1. Immunostaining was present in the cytoplasmic matrix, outer membrane of mitochondria, rough endoplasmic reticulum, multivesicular bodies and vesicles. Some nuclei of the cells were stained. 2.5-HT-li somata, dendrites and axons were postsynaptic to numerous unlabeled terminals which contained clear round vesicles (20-30 nm) or mixed with small granular vesicles (40-70 nm), large granular vesicles (90-110 nm) and flat clear vesicles. 3. The 5-HT-li axons were unmyelinated fibers, and the 5-HT-li axon terminals were scarce in the NRM. 4.5-HT-li axon terminals and dendrites abutting on capillaries and 5-HT-li dendrite-glial direct appositions were found in the NRM.These results revealed the ultrastructural characteristics of 5-HT-li neuron in the NRM. The variety of unlabeled terminals making contact with 5-HT-li somata and dendrites suggests that several neuronal system with possibly different transmitters may regulate 5-HT raphe-spinal neurons which may play integrative role in the NRM. Tae relationship between 5-HT neuron and the significance of the local microcirculation and the relationship between 5-HT neurons and glia cells were also discussed in the present paper.