Obesity increases nociceptive activation of the trigeminal system.
BACKGROUND
Obesity is a risk factor associated with several pain syndromes. However, the mechanisms underlying the association between obesity and pain are not known. The aim of this study was to test the hypothesis that obesity enhances neuronal responses to nociceptive stimulation within the trigeminal nucleus caudalis (TNC).


METHODS
Male and female C57BL/6J mice were fed a high-fat or regular diet from the time of weaning until 20 weeks of age. We then quantified neuronal activation by measuring Fos immunoreactivity within the TNC in response to a facial injection of a low dose of capsaicin (1 μg/10 μL).


RESULTS
We found that 0.01% capsaicin did not significantly increase Fos immunoreactivity in control mice fed a regular diet. In contrast, this low dose of capsaicin caused a 3.3-fold increase in Fos in the TNC in obese mice (p < 0.001).


CONCLUSIONS
These results support the hypothesis that diet-induced obesity in mice enhances nociceptive processing within the TNC. Diet-induced obesity may be a useful model for mechanistic studies. Future studies will improve our understanding of how obesity may contribute to trigeminal pain by sensitizing the trigeminal nociceptive system.
Department of Neurology, University of Iowa, USA.
H L
HL
Rossi
A K S
AK
Luu
J L
JL
DeVilbiss
A
A
Recober
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D059305:Diet, High-Fat / Q000009:adverse effects; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism; D059226:Nociceptive Pain / Q000503:physiopathology*; D009765:Obesity / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D014275:Trigeminal Caudal Nucleus / Q000187:drug effects / Q000378:metabolism*
D016760:Proto-Oncogene Proteins c-fos; D002211:Capsaicin