ABSTRACT
Objective To evaluate the role of T?type calcium channels in up?regulation of spinal Ca2+∕calmodulin?dependent protein kinase Ⅱ ( CaMKⅡ) expression in rats with neuropathic pain. Meth?ods Forty?eight male Sprague?Dawley rats, weighing 230-270 g, in which intrathecal catheters were suc?cessfully implanted, were divided into 4 groups ( n=12 each) using a random number table: sham opera?tion group (group S), neuropathic pain group (group NP), normal saline group (group NS), and T?type calcium channel blocker mibefradil group ( group M ) . The model of neuropathic pain was established by chronic compression of the dorsal root ganglion ( DRG) . Normal saline 20μl and mibefradil 200μg ( dilu?ted to 20μl in normal saline) were injected intrathecally at 5 days after compression of the DRG in NS and M groups, respectively. Before intrathecal catheter implantation ( T1 ) , before compression of the DRG ( T2 ) , at 5 days after compression of the DRG and before intrathecal administration ( T3 ) , and at 30, 60, 120 and 240 min after intrathecal administration ( T4?7 ) , the mechanical paw withdrawal threshold ( MWT) and thermal paw withdrawal latency ( TWL) were measured. The rats were sacrificed after the last measure?ment of the pain threshold at T7 , and the lumbar enlargement segments of the spinal cord were harvested for determination of CaMKⅡ expression by Western blot. Results Compared with group S, the MWT was significantly decreased, and TWL was significantly shortened at T3?7 , and the expression of spinal CaMKⅡ was significantly up?regulated in NP and M groups (P0.05). Conclusion T?type calcium channels are opened, the intra?cellular free calcium ion concentrations are increased, and activated spinal CaMKⅡ is involved in the de?velopment of neuropathic pain in rats.