Investigating the expression of metabotropic glutamate receptors in trigeminal ganglion neurons and satellite glial cells: implications for craniofacial pain.
OBJECTIVE
Previous studies have demonstrated that various subtypes of the metabotropic glutamate receptors (mGluRs) are expressed in the dorsal root ganglion (DRG) of the peripheral nervous system (PNS), implicating that glutamate potentially contributes to sensory transmission through these receptors. While mGluR expression has been investigated largely in the DRG, the present study focused on mGluR expression on neurons and satellite glial cells (SGCs) of the trigeminal ganglion (TG).


METHODS
To address the presence of mGluRs in rat TG neurons and their corresponding SGCs, the trigeminal ganglia from six adult male Wistar rats were isolated and immunohistochemistry and immunocytochemistry were performed. The expression of mGluR1α-, mGluR2/3- and mGluR8 on TG neurons and SGCs was investigated in tissue slices and isolated cells.


RESULTS
35.1 ± 6.0% of the TG neurons were positive for mGluR1α, whereas 39.9 ± 7.7% and 55.5 ± 6.3% were positive for mGluR2/3 and mGluR8, respectively. Immunoreactive neurons expressing mGluRs were mainly medium- to large sized, with a smaller population of small-sized neurons showing immunoreactivity. The SGCs showed immunoreactivity toward mGluR1α and mGluR8, but not mGluR2/3, both in the tissue and in isolated cells.


CONCLUSIONS
Findings from the present study showed that trigeminal neurons express mGluR1α, mGluR2/3 and mGluR8, while SGCs only express mGluR1α and mGluR8. This novel evidence may advance investigations on a possible role of mGluRs in relation to trigeminal pain transmission within the craniofacial region.
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Faculty of Medicine , Aalborg University, Frederik Bajers Vej, Aalborg East , Denmark.
Dennis
D
Boye Larsen
Gunda
G
Ingemann Kristensen
Vinodenee
V
Panchalingam
Jens Christian
JC
Laursen
Jeppe
J
Nørgaard Poulsen
Maria
M
Skallerup Andersen
Aginsha
A
Kandiah
Parisa
P
Gazerani
D000818:Animals; D005157:Facial Pain / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D009928:Organ Specificity; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000096:biosynthesis* / Q000378:metabolism; D027161:Satellite Cells, Perineuronal / Q000378:metabolism* / Q000473:pathology; D012668:Trigeminal Ganglion / Q000378:metabolism / Q000473:pathology
D018094:Receptors, Metabotropic Glutamate; C108822:metabotropic glutamate receptor 2; C111435:metabotropic glutamate receptor 8; C104077:metabotropic glutamate receptor type 1
Group I mGluR; group II mGluR; group III mGluR; neuron-glia interaction; sensory transmission; trigeminal ganglion