Effect of gabapentin on Cav3.2 channels in dorsal root ganglia of rats with neuropathic pain

Objective To evaluate the effect of gabapentin on Cav3.2 channels in the dorsal root ganglia (DRG) of rats with neuropathic pain. Methods Thirty male Sprague-Dawley rats, aged 6-7 weeks, weighing 225-275 g, were divided into 3 groups (n=10 each) using a random number table: sham operation group (S group), neuropathic pain group (NP group) and gabapentin group (G group). In NP and G groups, neuropathic pain was induced by chronic constriction injury to the left sciatic nerve.Starting from 7th day after operation, gabapentin 100 mg/kg in 1 ml of normal saline was injected intraperitoneally twice a day for 7 consecutive days in group G, and the equal volume of normal saline was given twice a day for 7 consecutive days in S and NP groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured on day 3 before operation and on postoperative days 3, 7 and 14.After the last measurement of pain thresholds on the postoperative day 14, 4 rats were sacrificed for determination of Cav3.2 mRNA expression (by real-time polymerase chain reaction) and Cav3.2 protein expression (by Western blot) in the DRG. Results Compared with S group, the MWT was significantly decreased, and TWL was significantly shortened on postoperative days 3, 7 and 14, and the expression of Cav3.2 protein and mRNA in the DRG was significantly up-regulated in group NP, and the MWT was significantly decreased, and TWL was significantly shortened on postoperative days 3 and 7 (P 0.05). Compared with NP group, the MWT was significantly increased, and TWL was significantly prolonged on the postoperative day 14, and the expression of Cav3.2 protein and mRNA in the DRG was significantly down-regulated in group G (P<0.05). Conclusion The mechanism by which gabapentin attenuates neuropathic pain may be related to inhibition of the function of Cav3.2 channels in the DRG of rats. Key words: Cyclohexanecarboxylic acids; Neuralgia; Calcium channels; Ganglia, spinal