Document Detail

Spontaneous behavioral responses in the orofacial region: a model of trigeminal pain in mouse.
MedLine Citation:
PMID:  22830495     Owner:  NLM     Status:  MEDLINE    
OBJECTIVES: To develop a translational mouse model for the study and measurement of non-evoked pain in the orofacial region by establishing markers of nociceptive-specific grooming behaviors in the mouse.
BACKGROUND: Some of the most prevalent and debilitating conditions involve pain in the trigeminal distribution. Although there are current therapies for these pain conditions, for many patients, they are far from optimal. Understanding the pathophysiology of pain disorders arising from structures innervated by the trigeminal nerve is still limited, and most animal behavioral models focus on the measurement of evoked pain. In patients, spontaneous (non-evoked) pain responses provide a more accurate representation of the pain experience than do responses that are evoked by an artificial stimulus. Therefore, the development of animal models that measure spontaneous nociceptive behaviors may provide a significant translational tool for a better understanding of pain neurobiology.
METHODS: C57BL/6 mice received either an injection of 0.9% saline solution or complete Freund's adjuvant into the right masseter muscle. Animals were video-recorded and then analyzed by an observer blind to the experiment group. The duration of different facial grooming patterns performed in the area of injection were measured. After 2 hours, mice were euthanized and perfused, and the brainstem was removed. Fos protein expression in the trigeminal nucleus caudalis was quantified using immunohistochemistry to investigate nociceptive-specific neuronal activation. A separate group of animals was treated with morphine sulfate to determine the nociceptive-specific nature of their behaviors.
RESULTS: We characterized and quantified 3 distinct patterns of acute grooming behaviors: forepaw rubbing, lower lip skin/cheek rubbing against enclosure floor, and hindpaw scratching. These behaviors occurred with a reproducible frequency and time course, and were inhibited by the analgesic morphine. Complete Freund's adjuvant-injected animals also showed Fos labeling consistent with neuronal activation in nociceptive-specific pathways of the trigeminal nucleus after 2 hours.
CONCLUSIONS: These behaviors and their correlated cellular responses represent a model of trigeminal pain that can be used to better understand basic mechanisms of orofacial pain and identify new therapeutic approaches to this common and challenging condition.
Marcela Romero-Reyes; Simon Akerman; Elaine Nguyen; Alice Vijjeswarapu; Betty Hom; Hong-Wei Dong; Andrew C Charles
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-07-25
Journal Detail:
Title:  Headache     Volume:  53     ISSN:  1526-4610     ISO Abbreviation:  Headache     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-08     Completed Date:  2013-12-19     Revised Date:  2014-07-29    
Medline Journal Info:
Nlm Unique ID:  2985091R     Medline TA:  Headache     Country:  United States    
Other Details:
Languages:  eng     Pagination:  137-51     Citation Subset:  IM    
Copyright Information:
© 2012 American Headache Society.
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MeSH Terms
Behavior, Animal*
Disease Models, Animal
Facial Pain / chemically induced,  complications,  physiopathology
Freund's Adjuvant / toxicity
Mice, Inbred C57BL
Proto-Oncogene Proteins c-fos / biosynthesis
Trigeminal Neuralgia / chemically induced,  complications,  physiopathology*
Trigeminal Nuclei / metabolism
Grant Support
Reg. No./Substance:
0/Proto-Oncogene Proteins c-fos; 9007-81-2/Freund's Adjuvant

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