[Effects of intrathecal lornoxicam on withdrawal thresholds of rats to mechanical and thermal stimuli].
OBJECTIVE
To assess the effects of intrathecal lornoxicam on the withdrawal thresholds of rats to mechanical and thermal stimuli.


METHODS
After approval of the animal ethic committee, 18 healthy male adult rats were randomly allocated on average to receive the intrathecal solvent (Group S) 20 tL, intramuscular lornoxicam (Group IM) 120 microg/20 microL or intrathecal lornoxicam (Group IT) 120 microg/20 microL, and to do the mechanical withdrawal threshold measured by Dynamic Planter Aesthesiometer (Ugo Basile, Italy). Another 18 rats were allocated similarly to do the thermal withdrawal threshold measured by Hargreaves Test (Ugo Basile, Italy). The basal value of withdrawal threshold was first recorded, and then the intrathecal solvent, intramuscular or intrathecal lornoxicam was injected, and the withdrawal threshold values were measured once more in the period of total 150 min with each 30 min as a time section. The Student-Newman-Keuls test was used to identify the differences between groups, with the SPSS11.5 package.


RESULTS
In Group S, there was no difference between the threshold values after intrathecally injecting solvent and the basal value. In Group IM, 30 min after injection, the mechanical and thermal threshold values reached the peak [(31.1 +/- 4.05) g, (20.82 +/- 2.15)], and were different as compared with the basal value (P < 0.05, P < 0.01). The mechanical and thermal withdrawal threshold values decreased to the basal level at 60 min and 90 min respectively. In Group IT, 10 min after injection, the mechanical and thermal withdrawal threshold values [(35.0 +/- 2.76) g, (26.72 +/- 3.75) s] were different when compared with the basal value (P < 0.01). The mechanical and thermal withdrawal threshold values decreased to the basal level at 90 min and 120 min respectively. There was no difference of the basal value among the three groups. But at 10, 30, 60 min after lornoxicam administrated, the mechanical threshold values of Group IT were obviously higher than those of Group S; and at 10, 30 min, it was significantly higher than that of Group IM. At 10, 30, 60, 90 min, the thermal thresholds of Group IT were markedly higher than those of the other groups.


CONCLUSIONS
Both systemic and intrathecal lornoxicam can elevate the withdrawal threshold values of rats to mechanical and thermal stimuli, but the onset of this effect is faster, and the maintenance is longer by intrathecal route.
Chen
Xu
X
Laboratory of Anesthesiology and Critical Disease, West China Hospital, Sichuan University, Chengdu 610041, China.
Yang
Bang-xiang
BX
Liu
Hui
H
Yang
Yong
Y
Xiao
Hong
H
D000818:Animals; D007278:Injections, Spinal; D008297:Male; D055595:Mechanical Phenomena; D017288:Pain Threshold / Q000187:drug effects*; D010894:Piroxicam / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature; D013997:Time Factors
D010894:Piroxicam; C059451:lornoxicam