Impaired basal thermal homeostasis in rats lacking capsaicin-sensitive peripheral small sensory neurons.
We studied the effects of selective loss of capsaicin-sensitive primary sensory neurons on thermosensation and thermoregulation in rats. Neonatal capsaicin treatment in rats caused a remarkable decrease in the number of small-diameter neurons in the dorsal root ganglion (DRG) compared with their number in the control rats. Gene expression analysis for various thermo-sensitive transient receptor potential (TRP) channels indicated marked reductions in the mRNA levels of TRPV1 (70%), TRPM8 (46%) and TRPA1 (64%), but not of TRPV2, in the DRG of capsaicin-treated rats compared with those in the control rats. In addition to the heat and cold insensitivity, capsaicin-treated rats showed lower rectal core temperature, higher skin temperature and decreased sensitivity to ambient temperature alteration under normal housing at room temperature, suggesting impaired thermosensation and change in thermoregulation in the rats. Uncoupling protein 1 (UCP1) expression and the thermogenic ability in brown adipose tissues were attenuated in the capsaicin-treated rats. These results indicate a critical role of capsaicin-sensitive sensory neurons in both heat and cool sensation and hence in basal thermal homeostasis, which is balanced by heat release and production including UCP1 thermogenesis, following sensation of the ambient temperature.
Yamashita
Hitoshi
H
Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Japan. hyamashi@isc.chubu.ac.jp
Wang
Zuocheng
Z
Wang
Youxue
Y
Furuyama
Tatsuo
T
Kontani
Yasuhide
Y
Sato
Yuzo
Y
Mori
Nozomu
N
D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001833:Body Temperature Regulation / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism; D008297:Male; D024101:Mitochondrial Proteins / Q000378:metabolism; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism; D022722:Thermogenesis / Q000187:drug effects; D013697:Thermosensing / Q000187:drug effects; D000071256:Uncoupling Protein 1
D007473:Ion Channels; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D050053:TRPM Cation Channels; D050916:TRPV Cation Channels; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; D002211:Capsaicin