大鼠中缝大核超微结构的观察

ULTRASTRUCTURAL OBSERVATIONS ON THE NUCLEUS RAPHE MAGNUS IN THE RAT

The ultrastructure of the rat nucleus raphe magnus (NRM) was observed under transmission electron microscope in the present study. Most of the neurons of the NRM were medium and small sized fusiform and triangular in shape, they had spherical or ellipsoid nuclei and rather high nucleo-cytoplasmic ratio. Nuclear rodlets which composed of parallel filaments could be seen in some fusiform NRM neurons. There were numerous organelles in the cytoplasm. Axonal terminals apposed to most neuronal bodies and formed axo-somatic synapses. The predominant type of these synapses was symmetric. Sometimes, rod-like or spine-like cytoplasmic protrusions could be seen on the neuronal bodies, they often made axo-somatic synapses with axonal terminals. The neuropil of the NRM was quite complex. It was formed by transverse sections of myelinated fibers, unmyelinated fibers, synapses, and neuroglia. The axo-dendritic synapses were the major synaptic type in the neuropil. The predominant type of these axo-dendritic synapses was also symmetric and asymmetric axo-dendritic synapses. Some axonal terminals were arranged parallel with dendrites and formed symmetric synapses. Beneath subsynaptic membrane of some postsynaptic bags, there were some electrical dense spherules or bands which formed subsynaptic dense bodies. There were. no typical axo-axonic synapses in the NRM, but the parallelly arranged axonal terminals were often seen. Most of the presynaptic bags contained clear spherical vesicles or mixed with flattened and granular vesicles. Some postsynaptic bags were filled with flattened vesicles, they were also often mixed with spherical and granular vesicles.