OBSERVATIONS OF SEROTONIN-, SUBSTANCE PAND LEUCINE-ENKEPHALIN-LIKE IMMUNOREACTIVE SYNAPTIC ORGANIZATION IN THE NUCLEUS RAPHE MAGNUS OF THE RAT BY IMMUNOELECTRON MICROSCOPY / 解剖学报

ABSTRACT

Immunoelectron microscopic technique was used in the present study to observe the serotonin (5-HT)-, substance P (SP)-, and leucine-enkephalin (L-Enk)-like immunoreactive ultrastructures in the nucleus raphe magnus (NRM) of the rat. 5HT-like immunoreactive (5-HT-LI) axonal terminals were found to form axosomatic, axo-dendritic, and axo-axonic synapses with non-5-HT-LI neuronal cell bodies, 5-HT-LI and non-5-HT-LI dendrites, and non-5-HT-LI axonal terminals respectively. Non-5-HT-LI axonal terminals formed axo-somatic and axo-dendritic synapses with 5-HT-LI neuronal cell bodies and dendrites. SP-LI (or L-Enk-LI) axonal terminals formed axo-somatic, axo-dendritic synapses with SP-LI (or L-Enk-LI) and non-SP-LI (or non-L-Enk-LI) neuronal cell bodies and dendrites, respectively. L-Enk-LI axonal terminals constituting axo-axonic synapses with L-Enk-LI axonal boutons were observed less frequently. The most common synaptic type made by 3 kinds immunoreactive profiles mentioned above was axo-dendritic synapses made by non-immunoreactive axonal terminals with immunoreactive dendrites. The majority of the immunoreactive axonal boutons were mainly filled by clear spherical vesicles, but sometimes were mixed with small number of flat and granular vesicles. The immunoreactive products were irregular electron-dense substances, and were located on both inner and outer surfaces of the vesicles, or on the surface of the membranous cell organelles in the cytoplasm, etc.