Relationship between cold hyperalgesia and trafficking of TRPM8 to cell membrane in dorsal root ganglion of rats with neuropathic pain / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the relationship between cold hyperalgesia and trafficking of transient receptor potential melastatin 8 (TRPM8) to cell membrane in the dorsal root ganglion (DRG) of rats with neuropathic pain (NP).Methods Ninety-six healthy male Sprague-Dawley rats,aged 10-12 weeks,weighing 250-280 g,were divided into sham operation group (S group,n=48) and NP group (n =48) using a random number table.NP was produced by chronic constriction injury to the sciatic nerve.The number of paw lifts on the cold plate and mechanical paw withdrawal threshold (MWT) were measured on 1 day before operation and 1,4,7,10 and 14 days after operation.Rats were sacrificed after behavioral testing,and ipsilateral DRGs of the lumbar segment (L46) were dissected tor detection of the expression of TRPM8 in total and membrane proteins by Western blot,and the ratio of TRPM8 expression in the membrane protein to that in the total protein (m/t ratio) was calculated.Results Compared with group S,the number of paw lifts on the cold plate was significantly increased,the MWT was decreased,the expression of TRPM8 in total and membrane proteins was up-regulated,and m/t ratio was increased on postoperative days 4,7,10 and 14 in group NP (P＜0.05 or 0.01).In group NP,the number of paw lifts on the cold plate was gradually increased with the prolongation of time after operation and reached the peak on postoperative day 10,maintaining at the peak until postoperative day 14;the MWT was gradually decreased and reached the lowest level on postoperative day 10,maintaining at the lowest level until postoperative day 14;the expression of TRPM8 in total and membrane proteins and m/t ratio were gradually increased with the prolongation of time after operation and reached the peak on postoperative day 10,maintaining at the peak level until postoperative day 14 (P＜0.01).Conclusion The mechanism underlying the development of cold hyperalgesia is related to enhanced trafficking of TRPM8 to cell membrane in DRGs of rats with NP.