Blocking the glial function suppresses subcutaneous formalin-induced nociceptive behavior in the rat.
This study examined whether glial cells in the trigeminal nucleus caudalis (Sp5C) were necessary for orofacial nociception and nociceptive processing induced by subcutaneously (s.c.) injection of 5% formalin into left mystacial vibrissae. The immunohistochemical, immunoelectron microscopical methods and behavior assessment were used in this study. Two hours after administration of carbenoxolone (CBX, a gap junction blocker) or fluorocistrate (FCA, a glail metabolic inhibitor) into the cerebellomedullary cistern, the nociceptive behavior and scratching-cumulative time reduced significantly (P<0.01). FCA attenuated obviously the expression of Fos/NeuN-immunoreactive (-IR) neurons (mean+/-S.E.M.=29+/-2.5) and Fos/glial fibrillary acidic protein (GFAP)-IR astrocytes (7.2+/-2.2) in Sp5C. CBX decreased the number of Fos/NeuN-IR neurons (25+/-1.7), but did not affect Fos/GFAP-IR astrocytes (16.2+/-5.4), compared with vehicle-preadministered rats (Fos/NeuN-IR neurons 135+/-4.2, and Fos/GFAP-IR astrocytes 25.8+/-4). Immunoelectron microscopy established that Cx32/Cx43 heterotypic gap junctions (HGJs) were present on junction areas between astrocytes and neurons within Sp5C. The number of HGJs increased significantly following formalin s.c. injection. It suggests that the Sp5C astrocytes may play an active regulating role in orofacial nociception via Cx32/Cx43 HGJs between astrocytes and neurons of Sp5C.
Lan
Li
L
Institute of Neurosciences, The Fourth Military Medical University, Changle West Road, Xi'an 710032, PR China.
Yuan
Hua
H
Duan
Li
L
Cao
Rong
R
Gao
Bei
B
Shen
Jing
J
Xiong
Yingfei
Y
Chen
Liang-Wei
LW
Rao
Zhi-Ren
ZR
D000818:Animals; D001522:Behavior, Animal; D002229:Carbenoxolone / Q000494:pharmacology; D002951:Citrates / Q000494:pharmacology; D004195:Disease Models, Animal; D004347:Drug Interactions; D005455:Fluorescent Antibody Technique / Q000379:methods; D005557:Formaldehyde; D017629:Gap Junctions / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010147:Pain Measurement / Q000379:methods; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000294:innervation*; D014277:Trigeminal Neuralgia / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D014278:Trigeminal Nuclei / Q000166:cytology
D002951:Citrates; D005904:Glial Fibrillary Acidic Protein; D016761:Oncogene Proteins v-fos; D005557:Formaldehyde; C007744:fluorocitrate; D010751:Phosphopyruvate Hydratase; D002229:Carbenoxolone