Galanin is a selective marker of the retrotrapezoid nucleus in rats

J Comp Neurol. 2009 Jan 20;512(3):373-83. doi: 10.1002/cne.21897.


The rat retrotrapezoid nucleus (RTN) contains CO(2)-activated neurons that contribute to the central chemoreflex and to breathing automaticity. These neurons have two known markers, the transcription factor Phox2b and vesicular glutamate transporter 2 (VGLUT2). Noncatecholaminergic galanin-immunoreactive (ir) neurons within a region of the lower brainstem that seems identical to what is currently defined as the RTN have been previously described. Here we ask whether these galanin-expressing neurons are the same cells as the recently characterized CO(2)-sensitive neurons of the RTN. By using in situ hybridization, we found that pre-pro-galanin (PPGal) mRNA is expressed by an isolated cluster of neurons that is co-extensive with the RTN as defined by a population of strongly Phox2b-ir neurons devoid of tyrosine hydroxylase (Phox2b(+)/TH(-) neurons). This bilateral structure contains about 1,000 PPGal mRNA-positive neurons in the rat. The PPGal mRNA-positive neurons were Phox2b(+)/TH(-) and as susceptible to destruction by the toxin [Sar(9), Met (O(2))(11)]-substance P as the rest of the RTN Phox2b(+)/TH(-) cells of the RTN. CO(2)-activated neurons were recorded in the RTN of anesthetized rats and were labeled with biotinamide. Many of those cells (7/17, 41%, five rats) contained PPGal-mRNA. In conclusion, galanin mRNA is a very specific marker of the glutamatergic Phox2b(+)/TH(-) neurons of the RTN, but galanin mRNA identifies only half of these putative central respiratory chemoreceptors.

Publication types

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

MeSH terms

  • Animals
  • Biomarkers / metabolism*
  • Chemoreceptor Cells / cytology
  • Chemoreceptor Cells / metabolism
  • Galanin / genetics
  • Galanin / metabolism*
  • Glutamic Acid / metabolism
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism
  • Male
  • Medulla Oblongata* / anatomy & histology
  • Medulla Oblongata* / metabolism
  • Neurons / cytology
  • Neurons / metabolism
  • Protein Precursors / genetics
  • Protein Precursors / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Respiratory Center / cytology
  • Respiratory Center / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Tyrosine 3-Monooxygenase / genetics
  • Tyrosine 3-Monooxygenase / metabolism
  • Vesicular Glutamate Transport Protein 2 / genetics
  • Vesicular Glutamate Transport Protein 2 / metabolism


  • Biomarkers
  • Homeodomain Proteins
  • NBPhox protein
  • Protein Precursors
  • Transcription Factors
  • Vesicular Glutamate Transport Protein 2
  • Glutamic Acid
  • Galanin
  • Tyrosine 3-Monooxygenase