title: Substance P neuronal organization in the median region of the interpeduncular nucleus of the cat: an electron microscopic analysis.
abstract: The localization of substance P-like immunoreactivity in the interpeduncular nucleus using the peroxidase-antiperoxidase technique, revealed that the median region of the interpeduncular nucleus was one area rich in substance P-like immunoreactive processes. The ultrastructural characteristics of these substance P-like immunoreactive processes and their organization within the middle zone of the median region of the interpeduncular nucleus was studied. Substance P-like immunoreactivity was found in the perikaryon of small neurons, and in proximal and small dendrites. The substance P-like immunoreactive cell bodies and proximal dendrites receive a variety of unlabeled synaptic terminals. The immunoreactive small dendrites usually formed the central component of a "rosette"-like formation with unlabeled terminals. A few immunoreactive small unmyelinated axons and boutons were also present in the neuropil. The substance P-like immunoreactive boutons contained mainly small round vesicles with some large dense-core vesicles. These substance P-like immunoreactive boutons were presynaptic to unlabeled dendritic profiles, and frequently to substance P-like immunoreactive dendritic profiles. They were also seen in apposition to unlabeled boutons. Substance P-like immunoreactive boutons were not found to synapse with the crest-like dendritic processes in this part of the interpeduncular nucleus. It is suggested on the basis of morphological features, that some of the unlabeled terminals synapsing on substance P-like immunoreactive dendrities, may be cholinergic in nature.
mesh_terms: D000818:Animals; D002415:Cats; D004027:Diencephalon / Q000378:metabolism; D007124:Immunoenzyme Techniques; D008636:Mesencephalon / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D013373:Substance P