Development of thermal nociception in rats

Michal Falcon, Danielia Guendellman, Alex Stolberg, Hanan Frenk, Gideon Urca*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In the present study, we show that hypersensitivity to noxious thermal stimulation can be seen clearly in developing rats. Rats, at postnatal days 3, 6, 9, 12, 15, 21 and 90 were tested for reflex responsiveness to noxious heat, using tail withdrawal from hot water as the assay. Thermal nociceptive thresholds are considerably lowered, relative to adults, up to postnatal day 12. Thresholds were 39, 37.5, 40.8, 43.3, 46.5, 45.2 and 47.2°C for the respective age groups. Enhanced sensitivity to suprathreshold noxious stimuli is seen in neonates up to postnatal day 15 (but not on day 9). Starting on day 21, sensitivity to noxious stimuli decreases with increasing age, as can be seen by the decrease in the slope of the temperature-response curve (system gain). Spinal transections at postnatal days 13, 17, 20, 60, or 100 did not produce a change in nociceptive thresholds in any of the age groups. In contrast, sensitivity to noxious stimulation (system gain) was enhanced by spinalization in rats 20 days of age or older. Based on these results we suggest that threshold elevation with increasing age most probably reflects changes in local spinal properties, while changes in responsiveness to suprathreshold noxious stimuli involves maturation of both spinal and descending supraspinal structures.

Original languageEnglish
Pages (from-to)203-208
Number of pages6
Issue number1
StatePublished - Sep 1996


FundersFunder number
Ministry of Immigration
Israel Academy of Sciences and Humanities
Israel Science Foundation


    • Hypersensitivity
    • Neonate
    • Rat
    • Reflex responsiveness
    • Thermal nociception


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