The influence of non-nociceptive factors on hot-plate latency in rats.
The hot plate is a widely used test to assess nociception. The effect of non-nociceptive factors (weight, sex, activity, habituation, and repeated testing) on hot-plate latency was examined. Comparison of body weight and hot-plate latency revealed a small but significant inverse correlation (light rats had longer latencies). Habituating rats to the test room for 1 hour prior to testing did not decrease hot-plate latency except for female rats tested on days 2 to 4. Hot-plate latency decreased with repeated daily testing, but this was not caused by a decrease in locomotor activity or learning to respond. Activity on the hot plate was consistent across all 4 trials, and prior exposure to a room-temperature plate caused a similar decrease in latency as rats tested repeatedly on the hot plate. Despite this decrease in baseline hot-plate latency, there was no difference in morphine antinociceptive potency. The present study shows that weight, habituation to the test room, and repeated testing can alter baseline hot-plate latency, but these effects are small and have relatively little impact on morphine antinociception.


CONCLUSIONS
This manuscript shows that non-nociceptive factors such as body weight, habituation, and repeated testing can alter hot-plate latency, but these factors do not alter morphine potency. In sum, the hot-plate test is an easy to use and reliable method to assess supraspinally organized nociceptive responses.
Gunn
Amanda
A
Department of Psychology, Washington State University Vancouver, Vancouver, Washington, USA.
Bobeck
Erin N
EN
Weber
Ceri
C
Morgan
Michael M
MM
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects; D008297:Male; D009043:Motor Activity / Q000502:physiology; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology* / Q000523:psychology*; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology*
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