Effect of axotomy on expression of NPY, galanin, and NPY Y1 and Y2 receptors in dorsal root ganglia and the superior cervical ganglion studied with double-labeling in situ hybridization and immunohistochemistry

Exp Neurol. 2000 Apr;162(2):361-84. doi: 10.1006/exnr.1999.7329.

Abstract

Using double-labeling techniques for both in situ hybridization and immunohistochemistry some peptides and peptide receptors were studied quantitatively in a sensory and a sympathetic ganglion after axotomy. In the lumbar 5 dorsal root ganglion (DRG) normally no neuropeptide Y- and only a few galanin-positive cell bodies are seen. Following complete transection of the sciatic nerve around 60% of all neuropeptide Y (NPY) neuron profiles (NPs) were galanin positive (+) and 33-44% of all galanin NPs were NPY(+). A good agreement between immunohistochemistry and in situ hybridization was observed for NPY and galanin. NPY Y1- and Y2-receptor (R) mRNAs were found in around 40% of all NPY mRNA(+) NPs, and more than half of the Y1-R mRNA(+) NPs and two-thirds of the Y2-R mRNA(+) NPs were NPY(+). In addition, more than one-third of the galanin mRNA-containing NPs showed colocalization with NPY receptor mRNAs and up to 70% of the Y2-R mRNA(+) NPs also expressed galanin mRNA. In the control superior cervical ganglion (SCG) 10% of the NPY(+) NPs were Y2-R mRNA(+), and 85% of the Y2-R(+) NPs were NPY mRNA(+), and the corresponding percentages after axotomy were around 35 and 45%, respectively. Following axotomy of the carotid nerves around half of all NPY(+) NPs were galanin(+), and conversely around 50% of all galanin NPs were NPY(+) at the mRNA level, whereas much lower percentages (15 and 9%, respectively) were observed with immunohistochemistry. These results demonstrate that double-labeling procedures are valid tools to quantitatively evaluate coexistence situations in sensory and sympathetic ganglia, showing a high degree of coexistence for NPY and galanin in axotomized neurons both in the lumbar 5 DRG and in the SCG. However, the immunohistochemical analysis in the SCG demonstrated much lower numbers of peptide-positive neurons than seen with in situ hybridization, suggesting that the latter technique is more sensitive. The fact that a considerable number of neurons express NPY together with Y1- and/or Y2-Rs indicates that both receptors may act as autoreceptors, the Y1-R presumably at the level of the cell body and the Y2-R on nerve terminals in the dorsal horn and/or the periphery. The present results also show that in both sensory and sympathetic neurons there is a strong upregulation of the Y2-R after nerve injury, suggesting a possible role in trophic and regenerative events.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axotomy
  • Galanin / biosynthesis*
  • Galanin / genetics
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / metabolism*
  • Ganglia, Spinal / surgery
  • Immunohistochemistry
  • In Situ Hybridization
  • Male
  • Neuropeptide Y / biosynthesis*
  • Neuropeptide Y / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Neuropeptide Y / biosynthesis*
  • Receptors, Neuropeptide Y / genetics
  • Sciatic Nerve / physiology
  • Sciatic Nerve / surgery
  • Superior Cervical Ganglion / cytology
  • Superior Cervical Ganglion / metabolism*
  • Superior Cervical Ganglion / surgery

Substances

  • Neuropeptide Y
  • RNA, Messenger
  • Receptors, Neuropeptide Y
  • neuropeptide Y2 receptor
  • Galanin