Role of T-type calcium channel in spinal neurotoxicity of intrathecal lidocaine in rats

Objective To investigate the role of T-type calcium channel in the spinal neurotoxicity of intrathecal (IT) lidocaine in rats.Methods Forty-eight adult male SD rats in which IT catheter was successfully implanted,weighing 230-270 g,were randomly divided into 4 groups ( n =12 each):dimethyl sulfoxide (DMSO)group (group D),lidocaine group (group L),mibefradil + lidocaine group (group M),normal saline + lidocaine group (group N).Another 12 rats served as control group (group C).DMSO and 10％ lidocaine 20μl were injected intrathecally in groups D and L respectively.After mibefradil 200 μg/10μl and normal saline 10 μl were injected intrathecally in groups M and N respectively,10％ lidocaine 20 μl was injected intrathecally in the two groups.The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured before IT injection and at 2,4,8 and 12 h and 1,2,3,4 and 5 d after IT injection (T0-9).Four rats were sacrificed at T6 in each group and their lumbar enlargements were removed for microscopic examination.Results Compared with group C,no significant change in MWT and TWL was found at each time point in group D,MWT was significantly increased at T1-8 and TWL was significantly prolonged at T1-7 in groups L and N,and MWT was significantly increased at T1-6 and TWL was significantly prolonged at T1-6 in group M ( P ＜ 0.05 ).Compared with groups L and N,MWT was significantly decreased at T1-4 and TWL was significantly shortened at T1-4 in group M ( P ＜ 0.05).Pathological injury was significantly reduced in group M as compared with groups L and N.Conclusion T-type calcium channel is involved in the spinal neurotoxicity of IT lidocaine in rats. Key words: Calcium channels, T-type; Lidocaine; Drug toxicity; Spinal cord