The Effect Of Toxoplasma Gondii Infection On Pain Behavior Of Mouse

Objective: Toxoplasma gondii,a protozoan parasite,is capable of infecting a broad range of intermediate hosts including humans.Its life cycle comprise asexual reproduction and sexual reproduction.And the parasite undergoes sexual reproduction only in the intestine of feline which is its only definitive host.Previously,a number of studies suggest that Toxoplasma gondii infection seems to be capable of altering a sequence of the natural behaviors of the host and can be as a risk factor for the development of some neuropsychiatric diseases,and thus to favor its accomplishment the whole life cycle.However,there are few studies even no study have reported the effect on pain behavior of toxoplasma gondii infection in its host.The aim of our study is to study the effect of toxoplasma gondii infection on pain behavior of mice..Methods: 1.We established the toxoplasma gondii infection in mice model by oral inoculating with cysts of toxoplasma gondii of Pru strain.At the meantime,we observed symptoms as well as found cysts in the brain.2.After we successfully established the toxoplasma gondii infection in mice model by oral inoculating with cysts of toxoplasma gondii of Pru strain.Then we respectively tested the pain behavior of the mice which infected with toxoplasma gondii post 0 week,4 weeks,8 weeks and 12 weeks and the wild type mice.3.After each time we finished testing the pain behavior of the mice which infected with toxoplasma gondii post 4 weeks,8 weeks and 12 weeks and the wild type mice,we immediately sacrificed the mice for collecting the serum samples and the brain samples respectively.The brain samples all were used to make homogenate in order to find cysts in the microscope which represented we successfully established the toxoplasma gondii infection in mice model.Thus we could use the serum samples to analyze pain mediators by enzyme-linked immunosorbent assay.4.After we finished testing the pain behavior of the mice which infected with toxoplasma gondii post 8 weeks and the wild type mice,immediately,we fixed their brain tissues by heart perfusion,and embeded them by paraffin to make tissue slices of the brain.Then we analyzed pain mediators in the certain brain stucture by immunohistochemistry.Results: 1.The mice which infected with the Pru strain of toxoplasma gondii post 10 days began to appear a number of symptoms,such as emaciation,ophthalmic disease,splenomegaly,hepatopathy,ascites,pilomotor fur,arch,cachexia,and anorexia.When the mice was infected with the Pru strain toxoplasma gondii post 25 days,these symptoms start to remission.In conclusion,we successfully established the toxoplasma gondii infection in mice model.2.The paw withdrawl mechanical threshold and the thermal pain threshold of the mice which infected with the Pru strain of toxoplasma gondii post 0 weeks,4 weeks,8 weeks and 12 weeks both significantly were higher than the control group.3.The concentration of SP,?-EP and 5-HT in the serum samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 4 weeks,8 weeks and 12 weeks have no difference in comparison to the control group.4.The expression of SP and ?-EP in the hippocampus of the brain samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 8 weeks both significantly were lower than the control group.The expression of SP significantly decreased and ?-EP significantly increased in the cortex of the brain samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 8 weeks in comparison to the control group.The expression of SP,?-EP and 5-HT in the hypothalamus of the brain samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 8 weeks all significantly increased in comparison to the control group.The expression of 5-HT and ?-EP in the amygdala of the brain samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 8 weeks both significantly increased in comparison to the control group.Conclusion: 1.As the mice which infected with the Pru strain of toxoplasma gondii appeared to a number of symptoms,we drawn a conculsion that we had successfully stablished the Pru strain of toxoplasma gondii infection in mice model.2.As a result of the paw withdrawl mechanical threshold and the thermal pain threshold of the mice which infected with the Pru strain of toxoplasma gondii post 0 weeks,4 weeks,8 weeks and 12 weeks both significantly were increased,we drawn a conculsion that toxoplasma gondii infection had an effect on pain behavior of mice.3.As a result of the concentration of SP,?-EP and 5-HT in the serum samples derived from the mice which infected with the Pru strain of toxoplasma gondii post 4 weeks,8 weeks and 12 weeks did not change,we drawn a conculsion that toxoplasma gondii infection had an effect on pain behavior,its mechanism might be not relevant to the concentration of SP,?-EP and 5-HT in the serum.4.As a result of the expression of SP in the hippocampus of the brain and in the cortex of the brain decreased,at the meantime,the expression of SP,5-HT and ?-EP in the hypothalamus of the brain,the expression of ?-EP in the cortex of the brain,and the expression of 5-HT and ?-EP in the amygdala of the brain all increased,we draw a conculsion that toxoplasma gondii infection had an effect on pain behavior,its mechanism might probably relevant to the expression of SP,?-EP and 5-HT in the hippocampus,cortex,hyppthalamus and amygdala of the brain.