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Effects of mibefradil administered intrathecally on the expression of nNOS in spinal cord of the rats following chronic compression of dorsal root ganglion

AIM:To investigate the effect of mibefradil administered intrathecally on the pain threshold and the expression of neuron nitric oxide synthase(nNOS)in the spinal cord of the rats following chronic compression of dorsal root ganglion.METHODS:The chronic compression of dorsal root ganglion(CCD)model was adopted.Three different doses of mibefradil,a T-type calcium channel blocker,were administered singly intrathecally to the rats after CCD 5 days.The mechanical withdrawal threshold(MWT)and thermal withdrawal latency(TWL)were determined with von Frey hair and thermal radiation apparatus before mibefradil administered and after mibefradil administered 30 min,60 min,120 min,240 min,and 480 min.Changes of nNOS expression in neurons of the spinal dorsal horn were detected by immunohistochemistry method,and the number of the nNOS positive neurons was counted under microscope.RESULTS:MWT and TWL declined significantly from the first day to the 21st day after CCD.Mibefradil administered intrathecally attenuated significantly both mechanical and thermal hyperagesia of the rats,and markedly inhibited the increase in the nNOS expression.CONCLUSION:These data show that T type calcium channel plays a key role in the CCD-induced mechanical and thermal hyperalgesia and possibly involves in the nNOS expression in the spinal.