The assessment of cold hyperalgesia after an incision.
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.
Scherer
Moritz
M
Department of Anaesthesiology and Intensive Care, University Hospital Münster, Albert-Schweitzer-Str. 33, 48149 Münster, Germany.
Reichl
Sylvia U
SU
Augustin
Miriam
M
Pogatzki-Zahn
Esther M
EM
Zahn
Peter K
PK
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