title: Ultrastructural localization of mu-1 opioid receptor in the dorsal raphe nucleus of the rat.
abstract: A simple pre-embedding avidin-biotin-peroxidase complex technique was used to study the ultrastructural localization of mu-1 opioid receptor in the rat dorsal raphe nucleus. Using low concentrations of the first antiserum for incubation with a short reaction time to 3,3'-diaminobenzidine, the immunostaining was faint at the light microscopic level. However, at the electron microscopic level strong immunoreaction was observed. Mu-1 opioid receptors were found to be localized on the postsynaptic membrane of dendrites, extra-synaptic plasma membrane, and the surface of the small, clear vesicles in axon terminals. Of the total 407 immunopositive profiles observed, 76.4% (311/407) were dendrites and 18.9% (77/407) were axon terminals. The immunostained myelinated axons and perikarya were relatively rare, with frequencies of 1.0% (4/407) and 3.7% (15/407), respectively. About 50.8% of the immunopositive dendrites (158/311) were immunostained having their MOR-LI results beneath the postsynaptic membrane, although about 19.6% of them (31/158) also exhibited MOR-LI on other components, including the extrasynaptic plasma membrane. Other immunopositive dendrites showed staining in some other contents, including extrasynaptic plasma membrane (82/311, 26.4%) or not on the plasma membranes (71/311, 22.8%). Less than half of the immunopositive axon terminals (35/77, 45.5%) were found to make synapses with nonimmunoreactive dendrites (31/77, 40.3%) or immunopositive dendrites (4/77, 5.2%); none were found to make synapses with immunoreactive perikarya. The present study shows that mu-1 opioid receptor in the dorsal raphe nucleus plays a role at both synapse or not.
authors.affiliation: Department of Anatomy, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Q P
authors.initials: QP
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Ochiai
authors.forename: J L
authors.initials: JL
authors.lastname: Guan
authors.forename: Y
authors.initials: Y
authors.lastname: Nakai
mesh_terms: D000818:Animals; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D007158:Immunologic Techniques; D008297:Male; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D011903:Raphe Nuclei / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D013194:Staining and Labeling; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014018:Tissue Distribution
chemical_list: D017450:Receptors, Opioid, mu