TY - JOUR
T1 - Development of thermal nociception in rats
AU - Falcon, Michal
AU - Guendellman, Danielia
AU - Stolberg, Alex
AU - Frenk, Hanan
AU - Urca, Gideon
N1 - Funding Information:
The present research was supported by a grant from the Israel Science Foundation, administered by the Israel Academy of Science and Humanities to H.F. A.S was in part supported by a post-doctoral fellowship of the Ministry of Immigration.
PY - 1996/9
Y1 - 1996/9
N2 - 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.
AB - 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.
KW - Hypersensitivity
KW - Neonate
KW - Rat
KW - Reflex responsiveness
KW - Thermal nociception
UR - http://www.scopus.com/inward/record.url?scp=0030245614&partnerID=8YFLogxK
U2 - 10.1016/0304-3959(96)03070-9
DO - 10.1016/0304-3959(96)03070-9
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AN - SCOPUS:0030245614
SN - 0304-3959
VL - 67
SP - 203
EP - 208
JO - Pain
JF - Pain
IS - 1
ER -