| Background and Objective:Seizure is considered as a series of central nervous system dysfunction caused by synchronized discharges of the brain neurons. Neurons' synchronized discharge is a kind of physical phenomena, and it could be regarded as electric energy spreading, but it's also a kind of biological phenomena. How can we understand the mechanism of energy spreading from the point of biologic view. In the study, an interferential effect of an electrode inserting into epileptogenic focus was investigated through observing behaviors of the rats, changes of EEG, changes of potential of the epileptogenic focus and expression of Cx43 in hippocampus of penicillin-induced epileptic rats.We setted up insulated electrode group at the same time for comparison, which should be help to further discussion of energy change during seizure process, and possibilities of antiepilepsy by conducting electric current out of the brain.Methods:We used hippocampal microinjection of penicillin to set up acute epilepsy model.50 SD rats were divided randomly into 4 large groups,10 subgroups and each group had 5 SD rats. As follows:1.Normal saline control groups(A):including 5 rats,the same dose of normal saline,and the rats were sacrificed at 24h.2.Penicillin-induced seizure model group(B):including 15 rats,1 hour after seizure onset subgroup(B1),3 hour after seizure onset subgroup(B3), 24 hour after seizure onset subgroup(B24),each group had 5 rats.The rats were sacrificed at 1,3,24h.3.Metal electrode interfering group(C):including 15 rats, metal electrode was inserted into epileptogenic focus.1 hour after seizure onset metal electrode subgroup(C1),3 hour after seizure onset metal electrode subgroup(C3),24 hour after seizure onset metal electrode subgroup(C24). The rats were sacrificed at 1,3,24h.4. Insulated electrode interfering group(D):including 15 rats, insulated electrode was inserted in epileptogenic focus.1 hour after seizure onset insulated electrode subgroup(D1),3 hour after seizure onset insulated electrode subgroup(D3),24 hour after seizure onset insulated electrode subgroup(D24). The rats were sacrificed at time points of 1,3,24h. Indexes:1.Behavior of the rats:①latent period, which meant the time from injection of penicillin to sezure onset(above Racine class 2)②Amplitude of seizure bursting at points of 1,3,14h.2. EEG:recording times of epileptic wave for lOminutes at points of 1,3h.3. Potential of the epileptogenic focus:recording potential of the epileptogenic focus at pointsof 0.25,1,3,24h.4. Expression of Cx43:The expression of Cx43 in hippocampus were measured by immunohistochemistry.Results:1.Behavieral changes:1.1 The latent period of seizue:the latent period of seizue of penicillin-induced seizure model group(B) was 12.52±4.18 minutes, the latent period of seizue of metal electrode interfering group(C) was 17.80±5.56 minutes and the latent period of seizue of insulated electrode interfering group(D) was 12.08±3.90 minutes. The latent period of seizue of metal electrode interfering group(C) was longer than the latent period of seizue of penicillin-induced seizure model group(B) (p<0.05).1.2 Amplitude of seizure bursts:The amplitude of seizure bursts were almost over or equal to Racine class 4 at the point of 1 hour and over or equal to Racine class 5 at the point of 3 hour in penicillin-induced seizure model group(B); the amplitude of seizure bursts were almost over or equal to Racine class 3-4 at the point of 1 hour and over or equal to Racine class 4 at the point of 3 hour in metal electrode interfering group(C); the amplitude of seizure bursts were almost over or equal to Racine class 3-4 at the point of 1 hour and over or equal to Racine class 5 at the point of 3 hour in insulated electrode interfering group(D).2. The changes of EEGThe changes of EEG in normal saline control group were similar to ones in normal rats. The record of the epileptic waves(record for 10 minutes):256.80±15.94 times were recorded at the point of 1hour after sezure onset and 372.20±45.19times were recorded at the point of 3hour in penicillin-induced seizure model group(B);190.60±20.21 times were recorded at the point of lhour and 298.00±37.70 times were recorded at the piont of 3hour in metal electrode interfering group(C);262.00±31.62 times were recorded at the point of lhour and 352.00±40.15 times were recorded at 3hour in insulated electrode interfering group(D). The times of epileptic waves of group C were clearly less than the times of group B (p<0.05); the times of epileptic waves of group C were clearly less than the times of group D (p<0.05);and there were no significant difference between groupB and D.3. The changes of electric potential of epileptogenic focusElectric potential of epileptogenic focus in group A was about 70-80mv; the electric potentials of epileptogenic focus group B, C and D at the time points of 0.5h, 1h,3h and 24h showed curve of a rising slowly to peak and then dropping to normal level; the electric potential of group C compared with group B were much lower at each time point (p<0.05).4. The expression of Cx43 in hippocampusThe positive cells(include A strocytes and Neurons) could be found in cortex and CA1,CA2,CA3,DG areas of hippocampus. The expressions of Cx43 in CA3 of hippocampus were significantly increased in group B, C and D compared with group A (p<0.05). At time point of 1,3,24h, there was no significant differences about the expression of Cx43 in CA3 of hippocampus between subgroup B3 and D3; but in subgroup C3, the expression of Cx43 was significantly decreased compared with subgroup B3 (p<0.05).Conclusions:1. The electric potential of epileptogenic focus raised slowly to a peak and then dropped to normal level during acute seizure process, the expression of Cx43 in hippocampus was associated with epilepsy in epileptic model during seizure.2. Prolonging the latent period of seizures, decreasing electric potential of epileptogenic focus and donwexpression of Cx43 in hippocampus indicated that metal electrodes may interfer with synchronization of epileptic activity.
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