title: A simplified up-down method (SUDO) for measuring mechanical nociception in rodents using von Frey filaments.
abstract: BACKGROUND
  The measurement of mechanosensitivity is a key method for the study of pain in animal models. This is often accomplished with the use of von Frey filaments in an up-down testing paradigm. The up-down method described by Chaplan et al. (J Neurosci Methods 53:55-63, 1994) for mechanosensitivity testing in rodents remains one of the most widely used methods for measuring pain in animals. However, this method results in animals receiving a varying number of stimuli, which may lead to animals in different groups receiving different testing experiences that influences their later responses. To standardize the measurement of mechanosensitivity we developed a simplified up-down method (SUDO) for estimating paw withdrawal threshold (PWT) with von Frey filaments that uses a constant number of five stimuli per test. We further refined the PWT calculation to allow the estimation of PWT directly from the behavioral response to the fifth stimulus, omitting the need for look-up tables.
  
  
  RESULTS
  The PWT estimates derived using SUDO strongly correlated (r > 0.96) with the PWT estimates determined with the conventional up-down method of Chaplan et al., and this correlation remained very strong across different levels of tester experience, different experimental conditions, and in tests from both mice and rats. The two testing methods also produced similar PWT estimates in prospective behavioral tests of mice at baseline and after induction of hyperalgesia by intraplantar capsaicin or complete Freund's adjuvant.
  
  
  CONCLUSIONS
  SUDO thus offers an accurate, fast and user-friendly replacement for the widely used up-down method of Chaplan et al.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Bonin
authors.forename: Cyril
authors.initials: C
authors.lastname: Bories
authors.affiliation: Unité de neurosciences cellulaires et moléculaire, Centre de recherche de l'Institut universitaire en santé mentale de Québec, 2601 Chemin de la Canardière, Québec, QC G1J 2G3, Canada. yves.dekoninck@neuro.ulaval.ca.
authors.forename: Yves
authors.initials: Y
authors.lastname: De Koninck
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000175:diagnosis* / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010146:Pain / Q000150:complications*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation / Q000009:adverse effects; D051381:Rats; D015203:Reproducibility of Results
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