The Regulatory Effect Of GABA_B Receptors In The Spinal Dorsal Horn And DRG In Rats With Paclitaxel-induced Neuropathic Pain On NF-kappa B Pathway

Objective: As a clinical first-line anticancer drugs,paclitaxel has a significant effect on a variety of malignant tumors.However paclitaxel-induced peripheral neuropathic pain that known as a dose-dependent neurotoxicity in the course of application,reducing the quality of life of patients,limiting its clinical application because of lacking of effective treatment.It has clinical significance and value to clarify the pathogenesis.In our study,rats with paclitaxel-induced neuropathy pain were induced by intraperitoneal injection of paclitaxel.To evaluate the role of GABA_B receptors in the regulation of nuclear factor kappa B pathway in spinal dorsal horn and dorsal root ganglion of rats with paclitaxol-induced neuropathic pain by intrathecally injection of gamma-aminobutyric acid B（GABA_B）receptor agonist baclofen or it’s inhibitor Saclofen,or NF-κB inhibitor SN50.Methods: The rats used in the study were purchased from the Animal Experimental Center of Hebei Medical University.They were healthy Pathogen-free male Sprague-Dawley rats and weighing 160-180 g.Rats with Paclitaxol-induced neuropathic pain were made by intraperitoneal injection of paclitaxel.Fourty Paclitaxol-induced neuropathic pain model rats whose PWT were equal to or less than 6 g were choosen and then randomly divided into four groups（n=10）according to the intrathecal administration: paclitaxel group（group P）: saline 10 μl;baclofen group（group B）: baclofen 0.5 μg/10μl;saclofen group（group S）: saclofen 30 μg/10μl;SN50 group（group SN）: SN50200 ng/10μl.Ten normal rats at the same moon’s age were choosen as the control group（group C）and then were intraperitoneal injected with constant volume solvent and intrathecal injected with 10 μl saline at the same timepoint.50% paw withdrawal mechanical threshold（PWT）was measured at the point T1（one day before intraperitoneal injection）,T2（one day before intrathecal prodrug）and T3（2 h after intrathecal administration）respectively.And then their spinal dorsal horn and DRG were moved.The changes in the expression of GABA_B1 receptor,NF-κBp65,IL-1β and TNF-α were determined by molecular biological methods.Results:1 Compared with point T1,PWT of all of the four groups were reduced at point T2（P<0.05）;compared with point T2,PWT of group B and group SN were increased at point T3（P<0.05）,while decreased in group S（P<0.05）.2 PCR results: GABA_B1 receptors in group P were down-regulated in spinal dorsal horn compared with group C,while up-regulated in DRG（P<0.05）compared with the group C.Meanwhile we can see the expression of NF-κBp65 and inflammatory factors IL-1β and TNF-α in group P were both up-regulated in spinal horn and DRG compared with group C（P<0.05）.Compared with group P,the expression of GABA_B1 receptor in group B was up-regulated both in spinal horn and DRG（P<0.05）,the expression of NF-κB p65 and inflammatory factors IL-1β and TNF-α were both down regulated（P<0.05）;the recepters and factors described above had an opposite expression in group S;the expression of GABA_B1 receptor was down regulated（P < 0.05）alone with the expression of NF-κBp65,IL-1β and TNF-αin group SN（P<0.05）.3 Western blot results: GABA_B1 receptor in group P were down-regulated in spinal dorsal horn compared with the group C,while up-regulated in the DRG（P<0.05）compared with the group C.Meanwhile we can see the expression of NF-κBp65 and inflammatory factor IL-1β and TNF-α in group P were both up-regulated in spinal horn and DRG compared with group C（P<0.05）.Compared with group P,the expression of GABA_B1 receptors in group B were up-regulated both in spinal horn and DRG（P<0.05）,the expression of NF-κB p65 and inflammatory factor IL-1β and TNF-α were both down regulated（P<0.05）;the recepters and factors described above hadan opposite expression in group S;the expression of GABA_B1 receptors were down regulated（P<0.05）alone with the expression of NF-κBp65,IL-1β and TNF-α in group SN（P<0.05）.Conclusion: The changes of GABA_B receptor expression and NF-κB are closely linked,play a common role in the occurrence and development of neuropathic pain.