The Mechanisms Of Spinal Microglia In Inflammatory Hyperalgesia

Partâ… the effect of intrathecal minocycline on CFA-induced arthritis inflammatory pain in rats.Objective To observe the effects of intrathecal(i.t) minocycline on inflammatory hyperalgesia in a rat model of CFA-induced arthritis.Methods 1.Behavioral response:After intrathecal catheter being implanted successfully between L₃ and L₄ vertebrae,adult male Sprague-dawley(SD) rats were pretreated with normal saline or 12.5,25,50μg different dose minocycline intrathecally 30 min prior to subcutaneously injection 50μl complete Freunds adjunvant(CFA) in the right tibio-tarsal joint.Intrathecal normal saline or minocycline was injected once daily for seven consecutive days.Paw withdrawal thermal latency(PWTL) and mechanical withdrawal threshold(MWT) were assessed for 14 successive days.Minocycline 50μg was been given intrathecally on day 2 and day 6 after CFA injection;Intrathecal minocycline 50μg or normal saline was injected 30 min prior to subcutaneously injection 50μl normal saline in the right tibio-tarsal joint.PWTL and MWT were assessed for 24 h.2.Morphologic study:Intrathecal normal saline or minocycline 50μg repectively 30 min prior to subcutaneously injection 50μl CFA in the right tibio-tarsal joint.Intrathecal normal saline or minocycline was injected once daily for seven consecutive days.The changes of spinal dorsal horn microglia,astroglia and neuron response to CFA-induced inflammatory pain were examined by immunohistochemisty methods of OX-42,GFAP and Fos after 4 hours following i.t normal saline or minocycline at 0,2,6 days and on 13 days.Results 1.In the behavioral responses detection:Intrathecal minocycline to noinflamed rats did not alter PWTL and MWT;PWTL was shortened and MWT was decreased after CFA-induced arthritis,pretreated and repeated intrathecal minocycline inhibited the shortening of PWTL and decreasing of MWT to seem in a does-dependent way in inflamed rats.Intrathecal minocycline 50μg inhibited reducing of PWTL and diminishing of MWT on day 2,but failed to alter on day 6 after CFA-induced inflammatory pain.2.Morphologic results:Pretreated and repeated intratheacl minocycline suppressed expressions of OX-42,GFAP and Fos in spinal dorsal horn after CFA-induced imflammatory pain.Intrathecal minocycline inhibited expression of OX-42 and GFAP on day 2,but failed to alter expression of GFAP on day 6 after CFA-induced arthritis.Conclusions Peripheral injection CFA induced spinal microglia activation;Pretreated and repeated intratheacl minocycline inhibited spinal microglia activation that could attenuate inflammatory hyperalgesia;Spinal microglia perhaps involved in inflammatory hyperalgesia.Partâ…¡The effect of Intratheacl minocycline on CFA-induced spinal proinflammatory cytokines in the ratObjective To investigate the expression levels of spinal proinflammatory cytokines in CFA-induced arthritis rats and the effect of intratheacl minocycline.Methods After intrathecal catheter being implanted successfully between L₃ and L₄ vertebrae, adult male Sprague-dawley(SD) rats were pretreated with normal saline or minocycline 50μg 30 min prior to subcutaneously injection of 50μl CFA in the right tibio-tarsal joint,intrathecal normal saline or minocycline was injected once daily for seven consecutive days.PWTL and MWT were assessed on 4h,2,6,13 days.The changes of spinal proinflammatory cytokines IL-1β,IL-6,TNF-αlevels were examined by ELISA analysis after 4 hours following intrathecal normal saline at 0,2, 6 days and on 13 days.after CFA injection.Results PWTL was shortened and MWT was decreased after CFA-induced inflammatory pain,pretreated and repeated intratheacl minocycline inhibited shortening of PWTL and decreasing of MWT. Expressions levels of IL-1β,IL-6 and TNF-αin the spine cord increased after 4 hours following intrathecal normal saline at 0,2,6 days and on 13 days after CFA injection, pretreated and repeated intratheacl minocycline markedly reduced increaseing of spinal IL-1β,IL-6 and TNF-αlevels in corresponding time point.Conclusions Peripheral injection CFA could induce the increasing of spinal proinflammatory cytokines levels;Pretreated and repeated intratheacl minocycline could reduce the increasing of CFA-induced spinal proinflammatory cytokines;Spinal microglia perhaps mediate the inflammatory hyperalgesia by proinflammatory cytokines.Partâ…¢The effect of Intratheacl minocycline on CFA-induced spinal Pp38MAPK in the ratObjective To investigate the expression of spinal Pp38MAPK in CFA-induced arthritis rats and the effect of intratheacl minocycline.Methods After intrathecal catheter being implanted successfully between L₃ and L₄ vertebrae,adult male Sprague-dawley(SD) rats were pretreated with normal saline or minocycline 50μg 30 min prior to subcutaneously injection 50μl CFA in the right tibio-tarsal joint, intrathecal normal saline or minocycline was injected once daily for seven consecutive days.PWTL and MWT were assessed on 4h,2,6,13 days after CFA injection.The changes of expression of spinal Pp38MAPK(phosphorylated p38 mitogen-activated protein kinase) were examined by Western blot analysis after 4 hours following i.t normal saline or minocycline on 0,2,6 days and on 13 days after CFA injection.Results PWTL was shortened and MWT was decreased after CFA-induced inflammatory pain,pretreated and repeated intratheacl minocycline inhibited shortening of PWTL and decreasing of MWT;Sham rats expressed low level Pp38MAPK;Expression of Pp38MAPK in the spine cord was increased after 4 hours following i.t normal saline or minocycline on 0,2,6 days and on 13 days after CFA injection,pretreated and repeated intrathecal minocycline markedly reduced up-regulation of Pp38MAPK levels of spinal cord in corresponding time point,but is increased compared with baseline level.Conclusions Peripheral injection CFA could induce the expression increasing of spinal Pp38MAPK;Pretreated and repeated intrathecal minocycline could inhibit expression of CFA-induced spinal Pp38MAPK; Spinal microglia perhaps mediated the inflammatory hyperalgesia by p38MAPK pathway.