An ultrastructural analysis of serotoninergic neurons in the nucleus raphe magnus of the rat.
The synaptic organization of serotonin elements in the nucleus raphe magnus of adult rat was investigated by electron microscopic immunocytochemistry with an antiserum against serotonin itself. Immunoreactive somata in the nucleus raphe magnus were usually of the same size (7-15 microns) and showed similar cytological features as their unlabeled congeners. The serotonin perikarya were contacted by a few unlabeled axon terminals containing round synaptic vesicles, and gave rise to dendrites which often ran perpendicularly to the midline. These dendrites received many contacts from axon terminals containing round or pleomorphic synaptic vesicles, but themselves failed to show vesicular aggregates or membrane differentiations suggestive of synaptic specialization. Immunoreactive axon terminals were numerous and mostly contained round or pleomorphic vesicles. Several exhibited synaptic contacts on dendrites, but there were also others which did not show any synaptic membranous differentiation, even when followed in serial sections. Immunostained myelinated as well as unmyelinated axons could be observed. These results provide a first description of the morphology and synaptic organization of the serotonin neurons in adult rat nucleus raphe magnus.
Chazal
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INSERM U6/CNRS URA 142, 280, Marseille, France.
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D000818:Animals; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D011903:Raphe Nuclei / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin