ABSTRACT
Objective To investigate the effects of intrathecal(IT)CX3 CR1 neutralizing antibody(antiFKR)on morphine tolerance in rats with bone cancer pain(BCP)and the unlerlying mechanism.Methods Forty-eight adult female SD rats aged 3 months weighing 180-200 g were randomized into 4 groups(n =12 each):group I sham operation(S); group Ⅱ BCP + normal saline(NS); group Ⅲ BCP + IgG(IgG)and group ⅣBCP + anti-FKR.Bone cancer pain(BCP)was induced by injecting Walker 256 cancer cells 10 μl(400 cells/ μl)into the medullary cavity of right tibia in groups Ⅱ,Ⅲ and Ⅳ.Ten days later morphine 20 μg/kg was administered IT twice a day for 7 consecutive days.Starting from the 8th day NS,IgG and anti-KFR 10 μl was administered IT once a day for 3 consecutive days in groups Ⅱ,Ⅲ and ⅣⅣ respectively.Paw withdrawal threshold to yon Frey filament stimulation(MWT)and paw withdrawal duration(MWD)were determined bcfore(To,baseline)and at 3,6,9 day after intra-tibial cancer cell inoculation(T1.2,3),on the 3rd and 7th day of IT morphine(T4.5)and on the 3rd day of IT NS/lgG/anti-KFR(T6).The animals were killed at T6 after last pain behavior assessment.The lumbar segment(L4-6)of the spinal cord was removed for determination of the expression of CX3 CR1 protein(by Western blot),μ-opioid receptor and TRPV1 receptor(by immuno-histochemistry)in the dorsal horn of spinal cord.Results IT morphine significantly eased BCP at T4,but morphine analgesia was significantly reduced on the 7th day of IT morphine in the 3 groups indicating morphine tolerance which was significantly relieved by anti-KFR in group Ⅳ.IT anti-KFR significantly down-regulated CX3CR1 prolein and TRPVI receptor expression and up-regulated μ-opioid receptor in group Ⅳ as compared with IT NS and lgG in groups Ⅱ and Ⅲ.Conctusion IT anti-KFR can relieve morphine tolerance in the rats with bone cancer pain by up-regulating μ-opioid receptor and down-regulating CX3 CR1 protein and TRPVI receptor expression.