The inhibition of the dorsal paragigantocellular reticular nucleus induces waking and the activation of all adrenergic and noradrenergic neurons: a combined pharmacological and functional neuroanatomical study

PLoS One. 2014 May 8;9(5):e96851. doi: 10.1371/journal.pone.0096851. eCollection 2014.

Abstract

GABAergic neurons specifically active during paradoxical sleep (PS) localized in the dorsal paragigantocellular reticular nucleus (DPGi) are known to be responsible for the cessation of activity of the noradrenergic neurons of the locus coeruleus during PS. In the present study, we therefore sought to determine the role of the DPGi in PS onset and maintenance and in the inhibition of the LC noradrenergic neurons during this state. The effect of the inactivation of DPGi neurons on the sleep-waking cycle was examined in rats by microinjection of muscimol, a GABAA agonist, or clonidine, an alpha-2 adrenergic receptor agonist. Combining immunostaining of the different populations of wake-inducing neurons with that of c-FOS, we then determined whether muscimol inhibition of the DPGi specifically induces the activation of the noradrenergic neurons of the LC. Slow wave sleep and PS were abolished during 3 and 5 h after muscimol injection in the DPGi, respectively. The application of clonidine in the DPGi specifically induced a significant decrease in PS quantities and delayed PS appearance compared to NaCl. We further surprisingly found out that more than 75% of the noradrenergic and adrenergic neurons of all adrenergic and noradrenergic cell groups are activated after muscimol treatment in contrast to the other wake active systems significantly less activated. These results suggest that, in addition to its already know inhibition of LC noradrenergic neurons during PS, the DPGi might inhibit the activity of noradrenergic and adrenergic neurons from all groups during PS, but also to a minor extent during SWS and waking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic Neurons / cytology*
  • Adrenergic Neurons / drug effects*
  • Adrenergic Neurons / metabolism
  • Animals
  • Clonidine / pharmacology
  • Medulla Oblongata / anatomy & histology*
  • Medulla Oblongata / cytology
  • Medulla Oblongata / drug effects*
  • Medulla Oblongata / physiology
  • Muscimol / pharmacology
  • Neuroanatomy*
  • Proto-Oncogene Proteins c-fos / metabolism
  • Rats
  • Sleep, REM / drug effects
  • Sleep, REM / physiology
  • Wakefulness / drug effects*
  • Wakefulness / physiology*

Substances

  • Proto-Oncogene Proteins c-fos
  • Muscimol
  • Clonidine

Grants and funding

This work was supported by INSERM, CNRS, University Claude Bernard Lyon 1 and the French ministry of research. O. Clément received a grant from the French ministry of research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.