Detection of cold pain, cold allodynia and cold hyperalgesia in freely behaving rats.
BACKGROUND
Pain is elicited by cold, and a major feature of many neuropathic pain states is that normally innocuous cool stimuli begin to produce pain (cold allodynia). To expand our understanding of cold induced pain states we have studied cold pain behaviors over a range of temperatures in several animal models of chronic pain.


RESULTS
We demonstrate that a Peltier-cooled cold plate with +/- 1 degrees C sensitivity enables quantitative measurement of a detection withdrawal response to cold stimuli in unrestrained rats. In naïve rats the threshold for eliciting cold pain behavior is 5 degrees C. The withdrawal threshold for cold allodynia is 15 degrees C in both the spared nerve injury and spinal nerve ligation models of neuropathic pain. Cold hyperalgesia is present in the spared nerve injury model animals, manifesting as a reduced latency of withdrawal response threshold at temperatures that elicit cold pain in naïve rats. We also show that following the peripheral inflammation produced by intraplantar injection of complete Freund's adjuvant, a hypersensitivity to cold occurs.


CONCLUSIONS
The peltier-cooled provides an effective means of assaying cold sensitivity in unrestrained rats. Behavioral testing of cold allodynia, hyperalgesia and pain will greatly facilitate the study of the neurobiological mechanisms involved in cold/cool sensations and enable measurement of the efficacy of pharmacological treatments to reduce these symptoms.
Allchorne
Andrew J
AJ
Neural Plasticity Research Group, Department of Anesthesia & Critical Care, Massachusetts General Hospital & Harvard Medical School, 13th Street, Building 149 (#4309), Charlestown, MA 02129, USA. andrew.allchorne@gmail.com
Broom
Daniel C
DC
Woolf
Clifford J
CJ
D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003080:Cold Temperature / Q000009:adverse effects*; D003714:Denervation; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000139:chemically induced / Q000175:diagnosis* / Q000503:physiopathology; D007249:Inflammation / Q000139:chemically induced / Q000150:complications / Q000503:physiopathology; D008026:Ligation; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000139:chemically induced / Q000175:diagnosis* / Q000503:physiopathology; D010147:Pain Measurement / Q000379:methods* / Q000592:standards; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D059348:Peripheral Nerve Injuries; D010525:Peripheral Nerves / Q000503:physiopathology*; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000503:physiopathology; D013127:Spinal Nerves / Q000293:injuries / Q000503:physiopathology; D014851:Wakefulness / Q000502:physiology