ABSTRACT
BACKGROUND: To investigate the pathophysiology of temperature hypersensitivity in neuropathic pain rodent models, it is essential to be able to quantify the phenotype as objective as possible. Current temperature sensitivity measuring paradigms are performed during exposure to external factors, i.e. light, sound and smell, which modulate behavior significantly. In addition the present outcome measure for temperature hypersensitivity in rodents is the examination of the hind paw lift upon exposure to a certain temperature, which reflects more a reflex-flexion than an experience of pain. NEW METHOD: Therefore the Rotterdam Advanced Multiple Plate (RAMP) was developed to assess cold hyperalgesia and allodynia objectively in freely behaving neuropathic pain rats, which measures the avoidance for certain temperatures and monitoring the location of the rat with an infrared camera while excluding external environmental influences such as light and sound. RESULTS: Compared to sham rats, the spared nerve injury (SNI) rats demonstrated a higher preference for the comfortable plate (27 °C) when the other three plates were set at 5 °C, 14 °C, 17 °C and 19 °C. We were unable to detect heat hyperalgesia and allodynia with the RAMP. COMPARISON WITH EXISTING METHOD: The paw withdrawal method displays similar results during cold hypersensitivity measurements as observed with the RAMP. The SNI group did display heat hypersensitivity during the paw withdrawal test. CONCLUSIONS: The results indicate that the RAMP is able to quantify cold hyperalgesia and allodynia in neuropathic pain rats while resolves some of the problems of conventional temperature sensitivity measuring paradigms in rodents.
Subject(s)
Cold Temperature/adverse effects , Hyperalgesia/diagnosis , Pain Measurement/methods , Pain Threshold/physiology , Wakefulness , Analysis of Variance , Animals , Disease Models, Animal , Hyperalgesia/etiology , Male , Neuralgia/complications , Pain Measurement/instrumentation , Psychophysics , Rats , Rats, Wistar , Reproducibility of Results , Time FactorsABSTRACT
PURPOSE: It is often assumed that cold intolerance is associated with abnormalities in the skin temperature due to changes in the blood flow of the hands. In this study, we determined whether patients with and without cold intolerance after a hand fracture or healthy controls have a diminished rewarming after a cold stimulus. METHODS: The severity of cold intolerance was evaluated using the Cold Intolerance Symptom Severity (CISS) questionnaire. To determine whether abnormal rewarming plays a major role in the underlying pathophysiology of cold intolerance, a cold-stress test was applied at a mean of 30 months (with a range of 11 mo) after the patients recovered from a hand fracture. A control group also underwent identical cold-stress testing for comparison. Temperature during the rewarming phase was measured using videothermography. RESULTS: Thirteen control subjects and 18 patients participated. Control subjects did not report any symptoms of cold intolerance (CISS score, 0) and no loss of sensibility was measured. The mean CISS score of all patients was 27.8; 9 patients scored above the cut-off value for normal cold intolerance. No significant differences were found in the rewarming patterns between (1) the affected and non-affected hand of the postfracture patients, (2) the dominant and non-dominant hand of the control subjects, and (3) the patients and controls. CONCLUSIONS: The results of this study revealed no relation between the severity of cold intolerance and rewarming patterns after cold stress testing. This might suggest that temperature regulation of the hands in post-fracture patients might not be responsible for the symptoms of cold intolerance, based on cold-stress test response.
