SUBSTANCE P NEURONS AND THEIR SYNAPTIC RELATIONS IN THE NUCLEUS RAPHE MAGNUS——AN IMMUNOELECTRON MICROSCOPIC STUDY / 解剖学报

ABSTRACT

Substance P-like immunoreactive (SP-li) cell bodies and processes and their synaptic relations with other neural elements in the nucleus raphe magnus (NRM) of rats were studied by electron microscope. The results showed that SP-li neurons are fusiform, oval and multipolar cells which distribute evenly over the nucleus. Immunostaining was present in the cytoplasmic matrix and membranes of mitochondria, endoplasmic reticulum and vesicles. Both unmyelinated and myelinated SP-li axons are found in the NRM. SP-li dendrites are numerous in the NRM. SP-li dendrites and somata are contacted by a variety of round, flat and granular vesicle-containing terminals. A central SP-li dendrite receivie convergent inputs from unlabelled axonal boutons is frequently seen in the NRM. SP-li terminals are presynaptic to the unlabelled dendrites, also some SP-li terminals are apposed or presynaptic to SP-li dendrites. Axo-axonic (SP-li) synapses were found in the NRM. The unlabelled presynaptic boutons contain clear round vesicles or mixed with granular vesicles. A central SP-li terminalis contacted by several unlabelled terminals is also found in the NRM.