The Effect Of Intrathecal Dexmedetomidine On Spinal Cord Toxicity Induced By Bupivacaine In Rats

Objective：To evaluate the effects of intrathecal dexmedetomidine on spinal cordtoxicity induced by bupivacaine in rats.Methods： Sixty-four SD rats(280～320g)in which intrathecal catheter wassuccessfully implanted without complications were randomly divided into4groups(n=16each):Control group(group C);Dexmedetomidine group(group D); bupivacainegroup(group B);Dexmedetomidine and bupivacaine group(group DB).In groupC,D,B,DB,norml saline30ul,norml saline20ul and Dexmedetomidine（1ug/kg）10ul,norml saline10ul and2%bupivacaine20ul,Dexmedetomidine（1ug/kg）10ul and2%bupivacaine20ul were injected respectively once a day for7consecutive days.Paw withdrawal threshold to mechanical stimulation(MWT)and paw withdrawallatency to thermal nociceptive stimulus(TWL)were measured after injected in eachgroup.The animals were sacrificed after measured.The lumbar segment（L4-5）of thespinal cord was removed for microscopic examination,detection of neuronalapoptosis(by TUNEL) and determination of caspase-3protein expression(byimmuno-histochemistry).Results：（1）Compared with group C，MWT was significantly increased andTWL prolonged,the apoptosis index and caspase-3protein expression weresignificant increased among group DB and B(P<0.05);There was no significantdifference in MWT,TWL,the apoptosis index and caspase-3protein expression amonggroup D(P>0.05);Compared with group B,MWT was significantly decreased andTWL shorten and the apoptosis index and caspase-3protein expression weresignificant decreased among group DB(P<0.05).（2）The morphology and structure of nerve cells showed no abnormalities amonggroups C, D; DB group showed slightly reduced nerve cells, a small cell body shrink,loosely arranged, showing perinuclear chromatin mild dissolution, only a smallvacuole formation; Nerve cells was partly soma shrinkage, visible perinuclearchromatin dissolved and disappeared, a large vacuole formation, visible nucleusdissolve disappear neurons among group B. Conclusion： Intrathecal dexmedetomidine can reduce spinal cord toxicityinduced by bupivacaine in rats,and inhibition of apoptosis in the spinal cord may beinvolved in the underlying mechanism.