title: The ultrastructure and organization of methionine-enkephalin immunoreactive profiles in the interpeduncular nucleus of the cat.
abstract: An ultrastructural analysis of the dorso-intermediate (CDIZ) and dorso-median zones (CDMZ) at the caudal end of the interpeduncular nucleus was undertaken. Serial vibratome sections were stained for met-enkephalin-like immunoreactivity by using the indirect antibody peroxidase-antiperoxidase method of Sternberger, and ultrathin sections were examined electron microscopically. Met-enkephalin-like immunoreactivity was observed in two different types of somata in the two regions. The dendritic architecture of the dorso-intermediate zone was characterized by the presence of many dendritic crests. A large number of these dendritic crests were immunostained for met-enkephalin. A variety of terminals was also seen in the CDIZ and CDMZ and they are categorized according to their vesicular morphology into three classes. One class contained mainly clear round vesicles. The met-enkephalin-like immunoreactive (MELI) terminal profiles in both regions were of this class and contained small round vesicles which were less than 35 nm in diameter. These MELI terminals appeared in significant numbers, sometimes in close proximity to unlabeled somata and dendrites. The dorso-median zone had, in addition, two more classes of terminals. One class was characterized by a large number of dense-cored vesicles--class II, and the other group had a large proportion of flat clear vesicles--class III. The possible neurochemical identities of some of the unlabeled terminals in relation to the MELI dendritic structures are discussed in the light of known neurochemically established afferent projections to the CDIZ and CDMZ of the interpeduncular nucleus.
mesh_terms: D000818:Animals; D002415:Cats; D003712:Dendrites / Q000648:ultrastructure; D004744:Enkephalin, Methionine / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008636:Mesencephalon / Q000378:metabolism / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000648:ultrastructure
chemical_list: D004744:Enkephalin, Methionine