The effect of acclimatization and ambient temperature on heat withdrawal threshold in rats.
BACKGROUND
Nociception in rats is frequently measured in terms of latency of withdrawal reaction to radiant heat (thermal nociceptive threshold). The aim of this study was to determine how much housing acclimatization and ambient temperature affect the results of thermal pain threshold testing.


METHODS
All experiments used adult male Wistar rats. Thermal pain thresholds were tested using the radiant heat withdrawal reaction at three different body sites: forepaws, hind paws and tail. Skin temperature was measured using an Infrared thermometer and ambient temperature was set at 18, 20, 24 or 26 °C.


RESULTS
The results demonstrate that (1) thermal pain threshold was inversely related to both ambient and skin temperature; (2) housing acclimatization and repeated testing had no effect on nociceptive thresholds at any of the three body sites; (3) a resting, cranio-caudal distribution, of nociceptive sensitivity was observed; (4) hind paws and tail were more sensitive to changes of skin and ambient temperature than forepaws.


CONCLUSIONS
These findings show the importance of recording laboratory conditions in experiments and their influence on results.
Third Faculty of Medicine, Department of Normal, Pathological and Clinical Physiology, Charles University in Prague, Czech Republic.
J
J
Vítková
M
M
Loučka
J
J
Boček
S
S
Vaculín
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D006358:Hot Temperature; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D012881:Skin Temperature; D013696:Temperature