Sub-regions of the dorsal raphé nucleus receive different inputs from the brainstem

Sleep Med. 2018 Sep;49:53-63. doi: 10.1016/j.sleep.2018.07.002. Epub 2018 Aug 2.

Abstract

The dorsal raphe nucleus (DRN) through its extensive efferent projections has been implicated in a great variety of physiological and behavioral functions including the regulation of the sleep-wake cycle. This nucleus is composed of five sub-regions defined according to the distribution of its serotonergic (5-HT) neurons. In addition to its heterogeneity in neuronal populations, the DRN contains a great diversity of 5-HT neuronal subtypes identified based on their electrophysiological characteristics, morphology and sub-regional distribution. This suggests that the DRN sub-regions may play different functional roles. Recent studies reported long-range inputs specific to the 5-HT neurons of the DRN; but they did not differentiate whether some inputs were specific to a DRN sub-region, or another region. To fulfill this gap, we have previously described the forebrain afferents to the different sub-regions of the DRN using cholera toxin b subunit and Phaseolus vulgaris-leucoagglutinin, as retrograde and anterograde tracers respectively. In the present work, we provide a detailed map of the brainstem projections to these different sub-regions. We show that if some brainstem structures project homogeneously to all sub-regions, most of the brainstem long-range inputs project in a topographically organized manner onto the DRN and, moreover, that a rich interconnected network is present within the DRN.

Keywords: Arousal; Mood disorders; Serotonin; Sleep.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Stem / physiology*
  • Cholera Toxin
  • Dorsal Raphe Nucleus / anatomy & histology
  • Dorsal Raphe Nucleus / pathology
  • Dorsal Raphe Nucleus / physiology*
  • France
  • Immunohistochemistry / methods
  • Male
  • Neural Pathways / anatomy & histology
  • Neural Pathways / physiology*
  • Neurons / physiology
  • Neurotransmitter Agents / physiology*
  • Phytohemagglutinins
  • Rats
  • Research
  • Serotonin / metabolism*
  • Wakefulness / physiology

Substances

  • Neurotransmitter Agents
  • Phytohemagglutinins
  • leukoagglutinins, plants
  • Serotonin
  • Cholera Toxin