Effect of calcitonin on analgesia and expression of calcitonin receptor in periaqueductal gray

Abstract

Objective To investigate the analgesic effect of salmon calcitonin(sCT)and its effect on expression of calcitonin receptor(CT-R)in periaqueductal gray(PAG). Methods Rat models of neuropathic pain were prepared by chronic constriction injury(CCI). Thermal withdrawal latency(TWL)and mechanical nociceptive threshold(MNT)were measured using hot plate test and yon Frey monofilaments test. The distribution of CT-R in PAG was detected by immunohistochemical method. CT-R protein was quantitatively determined by western blotting. Fourty male SD rats were randomized into 5 groups: normal group, sham-CCI group, CCI group, CCI plussubcutaneous sCT group, and CCI plus microinjection of sCT into PAG group. Results TWL, MNT, andexpression of CT-R in PAG showed no difference between normal group and sham-CCI group(P＞0. 05). TWL and MNT in CCI group were significantly lower than those in normal group(P＜0.05), and expression of CT-R in CCI group was significantly higher than that in normal group(P＜0.05). TWL, MNT and expression of CT-R in CCI rats increased significantly after sCT therapy(P＜0. 05), and the effect was more marked in PAG injection group than subcutaneous injection group(P＜0.05). Conclusions sCT raises the pain threshold and increase the expression of CT-R in PAG of CCI rats, while PAG injection showed more marked effect than subcutaneous injection. Key words: Calcitonin; Analgesia; Chronic constriction injury; Periaqueductal gray; Calcitonin receptor