Serotonergic System Modulation Of Itch And Analgesia Induced By Cholestasis In Rats

Objective:We first establish BDL rats model, and to determine the stability of the model, We first establish BDL rats model, and to determine the stability of the model, to explore 5- HT content in rat spinal cord and peripheral blood change and in5- HT receptor subtype expression changes in peripheral nervous system and central nervous system in the BDL rats.In BDL rats model, using the method such as pharmacology activation or block 5- HT receptor subtypes, to explore the endogenous 5- HT system regulation molecular mechanism of itching reaction and pain threshold increases.Methods:Male Sprague-Dawley rats were randomly divided into three groups: one group of bile duct ligation(BDL), another group of corresponding surgery treatment only,do not do bile duct ligation group(SHAM).Application of behavioral science, liver biopsy HE staining, the ALT kits and other technology, building success is determined.Application of high performance liquid chromatography(HPLC) to detect the5- HT content changes in rats peripheral nerve system and 5- HT content in the central nervous system tissue, at the same time, application of immunofluorescence chemical method to observe expression changes of 5- HT in the spinal cord.After building success,in a fixed point in time, the two groups of rats spin experiment was used to measure the mechanical pain, heat pain after BDL rats and other means to study the pain threshold of change.Building after success, at a fixed point in time, the two groups of rats using the cheek or on the back of the neck injection of the same dose of 5- HT(200 ug/rat)determined by behavioral science technology SHAM group with BDL group of 5- HT cause itching after reaction with building an extension of the time, itching degree of change. Again by means of pharmacology, one by one to activate or block 5- HT receptor subtype weeks outside expression changes in the nervous and central nervous system, to explore the endogenous 5- HT system regulation cholestasis rats itching reaction andmolecular mechanism of pain threshold increases.Results:(1) within 4 weeks after bile duct ligation( BDL) rats did not appear obvious itchy spontaneous reaction, but BDL rats induced by pain threshold and 5- HT itching reaction than the control group significantly increased(2)according to the results of immunofluorescence, 5- HT content in the spinal cord of BDL rats increased significantly than SHAM; HPLC results show BDL rats skin and 5- HT in the spinal cord levels higher than the control group obviously, and the 5- HT content was significantly lower in the blood.(3) Fluorescence quantitative PCR analysis found that the outer peripheral nervous system, including the dorsal root ganglion(DRG) and trigeminal ganglion(TG), and different 5- HT receptor subtypes have significantly raised, including 5- HT1 B, 5- HT1 D, 5- HT1 F, 5- HT2 A, 5- HT2 B, 5- HT3 A, 5- HT5, 5- HT6 and 5- HT7.By contrast, in the central nervous system, including the spinal cord and brain stem, different 5- HT receptor subtypes there had significantly lower, including 5- HT1 A, 5- HT1 F, 5- HT2 B,5- HT2 C, and 5- HT3 A, etc.(4)By adopting the means of pharmacology activation or block5- HT receptor subtypes, to explore the endogenous 5- HT system regulation cholestasis rats itching reaction and molecular mechanism of pain threshold increases.We found that intradermal injection of 5- HT2 agonists(a- methyl- 5- HT) and 5- HT7 agonists(LP44)in the control group and BDL group all can induce pruritus, and 5- HT3 A agonists(2-methyl- 5- hydroxytryptamine) only can induce pruritus in BDL group reactions. By intraperitoneal injection of consistent, 5- HT2 antagonists(Ketanserin) can inhibit itching reaction control and BDL group, and intraperitoneal injection of 5- HT3 A antagonists(Ondansetron and Azasetron) only can inhibit itching reaction BDL group. In the spinal cord level, intrathecal injection of 5- HT agonists, including 5- HT1A(DPAT), 5- HT2(a-methyl- 5- HT) and 5- HT3A(2- methyl- 5- hydroxytryptamine) and 5- HT7(LP44) can inhibit control and itchy BDL group rats behavior. Intrathecal injection of 5- HT1 A receptor antagonist(WAY- 100635) in the control group that inhibits BDL group rats itching, itching and 5- HT7 receptor antagonist(SB269970) can inhibit control and itchy BDL group rats behavior.In addition, intrathecal injection of 5- HT agonists, including 5-HT1A(DPAT), 5- HT2(a- methyl- 5- HT), and 5- HT3A(2- methyl- 5-hydroxytryptamine), as well as the system injection 5- HT2 receptor antagonist(Ketanserin) and 5- HT3 A receptor antagonist(Ondansetron and Azasetron) can inhibit BDL induced increase pain threshold. And intrathecal injection of 5- HT1 A agonist(DPAT)can reduce, and 5- HT1 A antagonists(WAY- 100635) can increase pain threshold in control rats.Conclusions:(1) In the BDL rats itch sensation sensitization and pain threshold increase;(2) In BDL rats, the content of 5- HT in skin and spinal cord tissue is increase,but reduce in plasma;(3) induced cholestasis dorsal root ganglion and trigeminal ganglion different 5- HT receptor subtype expression rise significantly, and in the spinal cord and brain stem, would have resulted in different 5- HT receptor subtype expression significantly lower;(4) related to cause itching 5- HT receptor mainly: 5- HT2 receptors and 5- HT7 and 5- HT3 A, outer weeks activate these three receptors could induce pruritus,while in the central activation can suppress itching behavior;(5) spinal cord 5- HT1 A, 5-HT2, 5- HT3 A, participate in the regulation of cholestasis induced pain threshold increases,but 5- HT7 effect is not obvious.