Galanin is a selective marker of the retrotrapezoid nucleus in rats.
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.
Stornetta
Ruth L
RL
Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA. rs3j@virginia.edu
Spirovski
Darko
D
Moreira
Thiago S
TS
Takakura
Ana C
AC
West
Gavin H
GH
Gwilt
Justin M
JM
Pilowsky
Paul M
PM
Guyenet
Patrice G
PG
D000818:Animals; D015415:Biomarkers / Q000378:metabolism*; D002628:Chemoreceptor Cells / Q000166:cytology / Q000378:metabolism; D019004:Galanin / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012125:Respiratory Center / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics / Q000378:metabolism
D015415:Biomarkers; D018398:Homeodomain Proteins; C109220:NBPhox protein; D011498:Protein Precursors; D014157:Transcription Factors; D050599:Vesicular Glutamate Transport Protein 2; D018698:Glutamic Acid; D019004:Galanin; D014446:Tyrosine 3-Monooxygenase