title: Neurotensin and substance P immunoreactive nerve endings in the guinea pig carotid sinus and their ultrastructural counterparts.
abstract: The carotid sinus of the guinea pig was analysed immunohistochemically for the occurrence of neuropeptides. Immunoreactivity (IR) for neurotensin (NT) and substance P (SP) is distributed in two different populations of nerve endings and varicosities. NT-IR fibers penetrate deeply into the tunica media of the elastic segment of the carotid sinus and form the large, branched lanceolate nerve terminals. Electron-microscopic investigations have revealed that the NT-IR varicosities correspond to the large afferent baroreceptor endings containing abundant mitochondria. SP-IR fibers are located mainly at the media-adventitial border. They seem to be correlated to dense-core, vesicle-containing varicosities identified in the electron microscope. Therefore, these fibers may constitute afferent and efferent perivascular plexus regulating the vascular tone of the carotid sinus wall.
mesh_terms: D000818:Animals; D002346:Carotid Sinus / Q000294:innervation* / Q000648:ultrastructure; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008854:Microscopy, Electron; D008928:Mitochondria / Q000648:ultrastructure; D009411:Nerve Endings / Q000032:analysis* / Q000648:ultrastructure; D009496:Neurotensin / Q000032:analysis*; D011311:Pressoreceptors / Q000648:ultrastructure; D013373:Substance P / Q000032:analysis*
chemical_list: D013373:Substance P; D009496:Neurotensin