Noradrenergic innervation of serotonergic neurons in the dorsal raphe: demonstration by electron microscopic autoradiography

Brain Res. 1981 Jan 5;204(1):1-11. doi: 10.1016/0006-8993(81)90646-6.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 5,7-Dihydroxytryptamine / pharmacology
  • Animals
  • Autoradiography
  • Axonal Transport
  • Brain Stem / physiology*
  • Fluoxetine / pharmacology
  • Hydroxydopamines / pharmacology
  • Male
  • Microscopy, Electron
  • Neurons / drug effects
  • Neurons / physiology*
  • Neurons / ultrastructure
  • Norepinephrine / metabolism*
  • Raphe Nuclei / physiology*
  • Raphe Nuclei / ultrastructure
  • Rats
  • Serotonin / metabolism*
  • Tritium


  • Hydroxydopamines
  • Fluoxetine
  • Tritium
  • 5,7-Dihydroxytryptamine
  • Serotonin
  • Norepinephrine