title: The assessment of cold hyperalgesia after an incision.
abstract: BACKGROUND
  Although cold hypersensitivity is a well-documented phenomenon in animals and humans with inflammatory and neuropathic pain, little is known about the presence of cold hyperalgesia after surgery. Therefore, we studied primary cold hyperalgesia after a surgical incision in mice.
  
  
  METHODS
  Before and after plantar incision, inflammation with complete Freund adjuvant, and spared nerve ligation, unrestrained male animals were placed on a Peltier-cooled cold plate with a surface temperature of 0 degrees C and withdrawal latencies were measured. Additionally, incision-induced cold hyperalgesia was also assessed in female animals. Furthermore, skin temperature before and after plantar incision and inflammation were assessed by using infrared thermography (Varioscan LW 3011; Infratec, Dresden, Germany).
  
  
  RESULTS
  Cold hyperalgesia to a noxious cold stimulus was observed after inflammation and nerve injury but not after a surgical incision. Similar results were demonstrated for female animals after incision. Furthermore, a significant increase in skin temperature was recorded after inflammation but not after incision, indicating that a surgery evokes only minor inflammatory effects.
  
  
  CONCLUSIONS
  The present data give strong evidence that a surgical incision does not cause cold hyperalgesia. Furthermore, a lack of cold hyperalgesia in unrestrained male and female mice after incision was not due to increased skin temperature after incision. Finally, we demonstrated that in contrast to a surgical incision, inflammation and nerve injury generate intense cold hyperalgesia and an increase in skin temperature, suggesting that different mechanisms are involved in surgical and inflammatory or neuropathic pain.
authors.affiliation: Department of Anaesthesiology and Intensive Care, University Hospital Münster, Albert-Schweitzer-Str. 33, 48149 Münster, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Scherer
authors.forename: Sylvia U
authors.initials: SU
authors.lastname: Reichl
authors.forename: Miriam
authors.initials: M
authors.lastname: Augustin
authors.forename: Esther M
authors.initials: EM
authors.lastname: Pogatzki-Zahn
authors.forename: Peter K
authors.initials: PK
authors.lastname: Zahn
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003080:Cold Temperature; D005260:Female; D018409:Foot Injuries / Q000150:complications; D006930:Hyperalgesia / Q000175:diagnosis* / Q000523:psychology; D007249:Inflammation / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010146:Pain / Q000523:psychology; D010147:Pain Measurement / Q000379:methods*; D010149:Postoperative Pain / Q000175:diagnosis* / Q000523:psychology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000473:pathology; D012867:Skin / Q000293:injuries; D012881:Skin Temperature; D013514:Surgical Procedures, Operative; D013817:Thermography