RESUMEN
Objective To investigate the effects of minocycline,a selective microglia inhibitor on dorsal GABAB receptor expression in the spinal cord in a rat model of neuropathic pain and the possible mechanism.Methods Forty-eight male SD rats weighing 220-260 g were used in this study.Neuropathic pain was induced by ligation of L5 spinal nerve(SNL).The animals were randomly divided into 4 groups(n=12 each):Ⅰ sham operation;Ⅱ SNL;Ⅲ sham operation+intrathecal(IT)minocycline 50 μg;IV SNL+IT minecycline 50 μg.Paw withdrawal threshold to von Frey hair stimulation was measured before operation(baseline)and at post-surgery days 1,2,4,6,8,10,12,14,16,18 in 6 animals in each group.The GABABR2 expression in dorsal horn of spinal cord was detected by Western blot at the time point when paw withdrawal threshold to mechanical stimulation was the lowest in another six animals which did not undergo yon Frey hair stimulation test.Results The paw withdrawal threshold to mechanical stimuli and the GABABR2 expression in the dorsal horn of spinal cord were significantly lower in SNL group than in sham operation group.The decreased paw withdrawal threshold to von Frey hair stimulation and the down-regulated GABABR2 expression in the spinal cord induced by SNL were ameliorated by intrathecal administration of micmglia inhibitor- minocycline in group Ⅳ.Conclusion The mechanism of neuropathic pain mediated by microglia activation may be related to the inhibition of GABAB receptor activation.