title: Ultrastructural examination of enkephalin and substance P input to cholinergic neurons within the rat neostriatum.
abstract: Enkephalin and substance P-containing inputs to cholinergic perikarya were examined in the rat neostriatum using an ultrastructural immunocytochemical double-labeling protocol. Sections of rat neostriatum were double-labeled for either choline acetyltransferase (ChAT) and substance P or ChAT and enkephalin using silver intensified colloidal gold and peroxidase as labels. Regions containing both ChAT-positive neurons and peroxidase reaction product were identified in the light microscope prior to sectioning for electron microscopy. Substance P-containing terminals which contained round synaptic vesicles and made symmetrical synaptic contacts were commonly observed in the neostriatum. Substance P synapses onto ChAT-positive perikarya and dendrites were frequently observed: up to 5 synaptic contacts were observed onto a ChAT-positive dendrite. Enkephalin labeling was also seen in a population of axon terminals containing round synaptic vesicles and exhibiting symmetrical synaptic specializations. In contrast to substance P-containing terminals, relatively few synaptic contacts were observed onto ChAT-positive labeled perikarya and dendrites although enkephalin-labeled terminals were seen in frequent contact with perikarya and dendrites of unlabeled spiny neurons. Since enkephalin and substance P are contained within different populations of striatal spiny neurons, the results of the present study suggest that these two types of neurons differ in their intrinsic striatal connections.
mesh_terms: D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D002795:Choline O-Acetyltransferase / Q000032:analysis*; D004745:Enkephalins / Q000032:analysis*; D008297:Male; D008854:Microscopy, Electron; D017072:Neostriatum / Q000737:chemistry* / Q000648:ultrastructure; D009474:Neurons / Q000737:chemistry* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000032:analysis*
chemical_list: D004745:Enkephalins; D013373:Substance P; D002795:Choline O-Acetyltransferase; D000109:Acetylcholine