Receptor gene expression of glucagon-like peptide-1, but not glucose-dependent insulinotropic polypeptide, in rat nodose ganglion cells

Auton Neurosci. 2004 Jan 30;110(1):36-43. doi: 10.1016/j.autneu.2003.11.001.

Abstract

We previously reported that afferent signals of the rat hepatic vagus increased upon intraportal appearance of insulinotropic hormone glucagon-like peptide-1(7-36) amide (GLP-1), but not glucose-dependent insulinotropic polypeptide (GIP). To obtain molecular evidence for the vagal chemoreception of GLP-1, the concept derived from those electrophysiological observations, receptor gene expressions of GLP-1 and GIP in the rat nodose ganglion were examined by means of reverse transcriptase-mediated polymerase chain reaction (RT-PCR) and Northern blot analysis. Gene expression of the GLP-1 receptor was clearly detected by both RT-PCR and Northern blot analysis. In situ hybridization study confirmed that the expression occurs in neuronal cells of the ganglion. As to the GIP receptor, RT-PCR amplified the gene transcript faintly though Northern blot analysis failed to detect any messages. However, semi-quantitative RT-PCR revealed that the ratio of the gene expression level of the GIP receptor to that of the GLP-1 receptor was less than 1:250, indicating that receptor gene expression of GIP is practically negligible in the ganglion. Additionally, an equal level of GLP-1 receptor gene expressions between left- and right-side ganglia was evidenced by semi-quantitative RT-PCR, implying possible extrahepatic occurrence of vagal GLP-1 reception in addition to the reception through the hepatic vagus (originating from the left-side ganglion). The present results offer, for the first time, the molecular basis for the vagal chemoreception of GLP-1 via its specific receptor.

MeSH terms

  • Animals
  • Blood Glucose / genetics
  • Blotting, Northern
  • Chemoreceptor Cells / metabolism
  • Functional Laterality / genetics
  • Gene Expression / genetics
  • Glucagon-Like Peptide-1 Receptor
  • In Situ Hybridization
  • Insulin / metabolism
  • Insulin Secretion
  • Liver / innervation
  • Liver / physiology
  • Male
  • Nodose Ganglion / cytology
  • Nodose Ganglion / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Wistar
  • Receptors, Gastrointestinal Hormone / genetics*
  • Receptors, Glucagon / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Visceral Afferents / metabolism

Substances

  • Blood Glucose
  • Glp1r protein, rat
  • Glucagon-Like Peptide-1 Receptor
  • Insulin
  • RNA, Messenger
  • Receptors, Gastrointestinal Hormone
  • Receptors, Glucagon
  • gastric inhibitory polypeptide receptor