| Object: To investigate the alterations of the neural transmission from vl PAG to PPN after chronic epilepsy developed by intraperitoneal injection of pilocarpine to induce status epilepticus.Methods: Healthy male adult Sprague-Dawley(SD)rats aged 4-5 weeks and weighing80-110 g were randomly selected and divided into two groups: group A,group B.Group A and group B were randomly divided into three groups: Control,Pilo and SE+Pilo groups.The SE+Pilo group was intraperitoneally injected with pilocarpine to induce status epilepticus(SE),Control group and Pilo group were injected with the same amount of normal Control of group A and group B.28 days later,all rats were stereotactically injected with FG to PPN.Two days later,the Pilo group and the SE+Pilo group were intraperitoneally injected again with pilocarpine to induce status epilepticus as a seizure stimulation,and Control group was intraperitoneally injected with the same amount of normal Control as false stimulation,then observe each group rats epileptic seizures status and activity.One hour later,the rats in group A were immediately perfused and fixed,and then the the c-Fos and vesicular glutamate transporter 1(Vesicular Glutamate Transporter 1(v GLUT1)in the vl PAG of each group were counted by immunofluorescence technique.The c-Fos or v GLUT1 labeled with reverse tracer fluorescent gold FG and the average immunofluorescence intensity of FG were counted.The expression levels of c-Fos and v GLUT1 in vl PAG region and c-Fos or v GLUT1 labeled with reverse tracer fluorescent gold FG were analyzed.Group B rats were tested by thermal needling apparatus to observe whether the pain threshold of the three groups was increased or decreased by(Paw Withdrawl Latency,PWL),which was used to observe whether the pain threshold of the three groups was increased or decreased.Fluoro Gold(FG),a retrograde tracing agent,was injected into PPN and its fluorescence detected in vl PAG to trace the neuronal projection from vl PAG to PPN.FG immunofluorescence intensity and FG traced neuron number were used to evaluate the neural transmission activity of vl PAG-PPN pathway.Immunohistochemistry of cFos and vesicular glutamate transporter 1(v GLUT1)were used to identify the activation of excitatory neural transmission from vl PAG to PPN.vl PAG-PPN neural transmission activity provoked by status epilepticus(SE)in na?ve rats(Pilo group)as well as in chronic epileptic rats(SE+Pilo group)was compared.All data were presented as mean ± standard error.ANOVA was used to compare the differences among the three groups.LSD-t test was used to compare the differences between the groups.P<0.05 was statistically significant and P<0.01 was statistically significant.Results:In group A: A large number of FG could be found in vl PAG in the Pilo group and the SE+Pilo group,and seizure stimulation caused a significant increase of the fluorescence intensity of FG-traced neurons labeled by c-Fos or by v GLUT1 in vl PAG both in Pilo group and in SE+Pilo group rats,and the difference was statistically significant(P<0.01).Within vl PAG,compared with the Pilo group,compared with Pilo group,the fluorescence intensity of FG-traced neurons labeled by c-Fos or by v GLUT1 in vl PAG was significantly decreased in SE+Pilo group rats,the number of c-Fos and v GLUT1 was significantly reduced,and the number of FG-traced neurons labeled with c-Fos or with v GLUT1 were also significantly reduced in the SE+Pilo group,but significantly higher than that of the Control group,the difference was statistically significant(P<0.01).In group B:The paw withdrawl latency(PWL)was significantly shorter in the SE+Pilo group than that in the Pilo group,but significantly longer than that in the Control group,with statistical significance(P<0.01).Conclusion: Seizures activate the excitatory conduction of vl PAG-PPN pathway,reduce pain sensitivity and increase pain threshold,while the excitatory conduction of vl PAG-PPN pathway weakens,enhances pain sensitivity and decreases pain threshold after chronic seizures.Thus,attenuated excitatory transmission of vl PAG-PPN pathway is associated with chronic epilepsy,implicating an involvement of this excitatory transmission in the comorbid relationship between epilepsy and migraine. |
PDF Full Text Request