Objective To evaluate the effect of neuropathic pain on the expression of GABAB receptor subtypes in spinal cord of rats with chronic constriction injury.Methods 36 rats were divided into Sham group and CCI group respectively.In CCI group,the left common sciatic nerve of anesthetized rats was exposed,four silk ligatures（30） were tied loosely proximal to the sciatica’s trifurcation.In Sham group,Sham surgery was undergone by exposing the left sciatic nerve without ligation.Hind paw thermal withdrawl latency（TWL） to thermal stimulus and mechanical withdrawl threshold（MWT） of mechanical stimulus were recorded before ligation or on 1 d,3 d,5 d,7 d,10 d,14 d,21 d,28 d after ligation respectively（n=8）.Expression of GABAB receptor subtypes were detected before ligation and 1 d,3 d,7 d,14 d,28 d after ligation respectively using bothe immunohistochemical assay（n=6） and Western blot technique（n=4）.Results There were no significant differences on the values of MWT and TWL before ligation between Sham group and CCI group.Compared with Sham group,the MWT and TWL of rats in CCI group significantly decreased after ligation（P<0.01,P<0.05） and continued to be decreased until 28 d after ligation.Both immunoreactive neurons and protein content of GABAB1a or GABAB2 subtypes increased on the 3rd day after ligation,then both decreased on the 7th day after ligation,and lasted for 28 dafter ligation.（P<0.01,P<0.05）.There were no changes of GABAB1b after ligation（P>0.05）.Conclusion There existed differences among expression of spinal GABAB receptor subtypes on rats with chronic constriction injury induced neuropathic pain.The expression of spinal GABAB1a and GABAB2 decreased while there were no changes of GABAB1b on neuropathic rats.
