The Possible Mechanism Of P2X4 Receptor In Rat Tibial Bone Cancer Pain

Part one: The changes of P2X4 receptor in rat tibial bone cancer painObjective To investigate the changes of P2X4 receptor in rat tibial bone cancer pain.Methods 28 female SD rats weighing 160～180g were randomly divided into 3 groups: Control group(K,n=8),Sham-operated group(J,n=8),Model group(M,n=12).K group was not given any treatments,J and M groups were respectively injected 10μlPBS solution or Walker 256 breast cancer cells(1×107/ml) into the left proximal tibial medullary cavity.At the day before and 3,6,9,12,15,18d after the operation, response of the left hind paw to mechanical stimulation with von-Frey filament and the difference of weight bearing between two hind paws were measured.Four rats were respectively executed at the twelfth days after the operation of K and J groups, the sixth,twelfth and eighteenth days after the operation of M group,to observe the P2X4 receptor expression in L4～6 from spinal cord tissue by immunohistochemical methods.Results The mechanical hyperalgesia emerged after estalishing model 6d and became more and more severe.At the same time, the expression,positive NUM and IOD of P2X4 receptor in spinal cord dorsal horn were significantly increased.The results were statistically significant difference from K and J groups(P<0.05).Conclusion P2X4 receptor,expression in spinal cord,may be involved in the generation and maintenance of rat tibial bone cancer pain. Part two: Effects of lntrathecal TNP-ATP and PPADS in rat model of tibial bone cancer pain on the expression of P2X4 receptor and pERK in spinal cord dorsal hornObjective To observe the effection of intrathecal injection TNP-ATP and PPADS in rat model of tibial bone cancer pain and the expression of P2X4 receptor and pERK in spinal cord dorsal horn, then explore its possible mechanisms.Methods 40 female SD rats weighing 160～180g were randomly divided into 5 group(sn=8): Sham-operated group(K group),Model group(M group),ddH2O group,TNP-ATP group and PPADS group.Sham-operated group was injected 10μl PBS solution into the left proximal tibial medullary cavity.Other groups was injected Walker 256 breast cancer cells (1×107/ml) 10μl into the left proximal tibial medullary cavity.Set pipes into subarachnoid space of all rats after establishing model five days,ddH2O group was intrathecal injected ddH2O 10μl, TNP-ATP group was intrathecal injected TNP-ATP (30nmol) 10μl and PPADS group was intrathecal injected PPADS (100nmol) 10μl,other two groups were not intrathecal injected anything for 5 days from the seventh day after establishing model.At the day before and 3,6,9,12d after modeling, response of the left hind paw to mechanical stimulation with von-Frey filament and the difference of weight bearing between two hind paws were measured.Rats were killed after the twelfth day of establishing model and L4～6 lumbar segment of the spinal cord were removed for determination of P2X4 receptor and pERK expression in the spinal cord dorsal horn by immunohistochemical methods.Results MWT,the difference of weight bearing between two hind paws,the expression of positive NUM and IOD of P2X4 receptor and pERK of PPADS group were significantly increased after intrathecal injected PPADS,the results were statistically significant difference from sham-operated group,but no difference from model group;While the results of TNP-ATP group were statistically significant difference from both sham-operated group and model group (P<0.05).Conclusion Both P2X4 receptor and pERK,expression in spinal cord,may be inhibitted to a certain extent after intrathecal injected TNP-ATP,while PPADS group did not have this effection.P2X4 receptor-ERK signal transduction pathway may play an important role in rat tibial bone cancer pain.