title: Noradrenergic innervation of serotonergic neurons in the dorsal raphe: demonstration by electron microscopic autoradiography.
abstract: In this study, noradrenergic (NE) terminals in the dorsal raphe were identified by [3H]NE electron microscopic (EM) autoradiography. Lesioning of NE terminals by treatment with the selective catecholamine neurotoxin, 6-hydroxydopamine produced a marked decrease in NE-labelled terminals. [3H]5-HT EM autoradiography of the dorsal raphe produced labelling of cell bodies, dendrites and axons but labelled terminals with synaptic junctions were not observed. Serotonergic (5-HT) neurons were identified at an early stage of degeneration following treatment with the selective 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). When both [3H]NE autoradiography and 5,7-DHT lesioning were combined, a majority of NE-labelled terminals, which formed synaptic specializations, innervated degenerating dendrites. These findings suggest that NE terminals directly innervate 5-HT cells in the dorsal raphe.
mesh_terms: D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001370:Axonal Transport; D001933:Brain Stem / Q000502:physiology*; D005473:Fluoxetine / Q000494:pharmacology; D006892:Hydroxydopamines / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D009638:Norepinephrine / Q000378:metabolism*; D011903:Raphe Nuclei / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D014316:Tritium
chemical_list: D006892:Hydroxydopamines; D005473:Fluoxetine; D014316:Tritium; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D009638:Norepinephrine