Retrotrapezoid nucleus, respiratory chemosensitivity and breathing automaticity

Respir Physiol Neurobiol. 2009 Aug 31;168(1-2):59-68. doi: 10.1016/j.resp.2009.02.001. Epub 2009 Feb 13.


Breathing automaticity and CO(2) regulation are inseparable neural processes. The retrotrapezoid nucleus (RTN), a group of glutamatergic neurons that express the transcription factor Phox2b, may be a crucial nodal point through which breathing automaticity is regulated to maintain CO(2) constant. This review updates the analysis presented in prior publications. Additional evidence that RTN neurons have central respiratory chemoreceptor properties is presented, but this is only one of many factors that determine their activity. The RTN is also regulated by powerful inputs from the carotid bodies and, at least in the adult, by many other synaptic inputs. We also analyze how RTN neurons may control the activity of the downstream central respiratory pattern generator. Specifically, we review the evidence which suggests that RTN neurons (a) innervate the entire ventral respiratory column and (b) control both inspiration and expiration. Finally, we argue that the RTN neurons are the adult form of the parafacial respiratory group in neonate rats.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Carbon Dioxide / metabolism
  • Chemoreceptor Cells / physiology*
  • Homeodomain Proteins / metabolism
  • Hydrogen-Ion Concentration
  • Models, Biological
  • Nerve Net
  • Phrenic Nerve / physiology
  • Respiration*
  • Respiratory Center / cytology*
  • Respiratory Center / physiology*
  • Transcription Factors / metabolism


  • Homeodomain Proteins
  • NBPhox protein
  • Transcription Factors
  • Carbon Dioxide