Effects Of Mental Electrode On The Expression Of GFAP In Hippocampus Of Penicillin-induced Seizure Rats In Different Phases

Background and Objective: Epilepsy is a common neurologic disorder. In China, there are about 9,000,000 people with epilepsy, and nearly 400,000 cases of epilepsy increase every year. Except for the side effects of antiepileptic drugs, about 25% of all the patients would suffer from refractory epilepsy. Therefore developing the further understanding of pathogenesis of epilepsy and finding new treatment methods are of great importance. In the previous studies, we found that electrodes insertion into the epileptic foci had the potential of anti-epilepsy function. In this study, effects of met al electrodes insertion on seizure onsets were further investigated through observing the expression of GFAP in hippocampus of penicillin-induced seizure rats and the hypotheses of inhibitory barrier breakthrough were discussed as well.Methods: 42 SD rats are divided into 7 groups, each group includes 6 rats. Each group was manipulated as following: (1) Normal saline control group (A); (2) Pre-convulsion group (B1); (3) Convulsion group (B2); (4) Post-convulsion group (B3); (5) Pre-convulsion of interfering with electrodes group (C1); (6) Convulsion of interfering with electrodes group (C2); (7) Post-convulsion of interfering with electrodes group (C3). The 7 groups were evaluated in behavior, latent period of seizures (time from penicillin injection to seizure to Racine grade 2 or above), the intensity of seizure, frequency of fits during five minutes at 0 h, 1 h, 2 h and the changes of EEG after seizures were induced. All the rats were sacrificed at specified time points and brain tissue was prepared for GFAP-immunoreactive tests. The expression of GFAP in hippocampus was analyed with immunohistochemical method, and MOD of GFAP immunoreaction in astrocytes was analyzed by using image analysis software (Image-Pro Plus 6.0).Results:1. The acute epileptic model was successfully induced with penicillin micro-injection into the right hippocampus. The success rate of seizure was 91.7%. 2. Behavioral changeslatent period of seizures: In penicillin induced-seizure groups (B2 and B3), seizures above Racine 2 emerged at 12.50±4.17 minutes after injection of penicillin. After emplacing the met al electrodes (C2 and C3), seizures above Racine 2 emerged at 17.08±5.50 minutes after penicillin injection. Compared with penicillin injection groups (B2 and B3), the latent periods of epilepsy in electrodes insertion groups (C2 and C3) were prolonged (P<0.05).Intensity of seizures: In penicillin induced-seizure groups (B2 and B3), at 0 h after seizure onset, the intensity of seizures were at Racine 2～3 in the majority of rats. At 1 h after seizure onset, the intensity of seizure was at Racine 4 in of rats. At 2 h after seizure onset, the intensity of seizure was at Racine 4 in the majority of rats, but an enhancement of Racine 5 were obvious; In electrodes insertion groups (C2 and C3), at 0 h after seizure onset, the intensity of seizures was at Racine 2 in the majority of rats. At 1 h after seizure onset, the intensity of seizure was at Racine 2 in majority of rats, but a slight enhancement of Racine 3 was observed. At 2 h after seizure onset, the intensity of seizure was at Racine 3～4 in the majority of rats.Frequency of fits: The frequencies of seizures were increased from 0 h to 2 h in both penicillin induced-seizure groups (B2 and B3) and electrodes insertion groups (C2 and C3), and electrodes insertion had no significant effects on reducing the frequencies of seizures.3. The changes of EEGMain waves in normal rats EEG wereα,βwaves, occasionallyθwaves. After injection of normal saline, wave amplitudes were decreased, but no epileptic waves were seen. In groups B1, B2 and B3, in the pre-convulsion phase, most of the epileptic waves were paroxysmal sharp waves and spike waves. At 2 h after seizure onset, persistent sharp waves, spike waves, sharp and slow wave complexes were showed mainly on EEG, with middle and high wave amplitude. At post-convulsion phase (24 h after seizure), low amplitude epileptic waves could still be found on EEG, although there were no behavioral epileptic seizures. In groups C1, C2 and C3, the frequenies of epileptic waves were decreased. 4. The results of immunohistochemistryIn all the groups, GFAP-immunoreactive astrocytes can be seen in CA1, CA3, DG and cortex. Positive cells were brown with branching processes and like the spiders. Observing CA3 of hippocampus with relatively more positive cells. There were no significant differences of the expression of GFAP in CA3 of hippocampus among the groups A, B1, B3, C1 and C3 (P>0.05). The expressions of GFAP in CA3 in B2 and C2 were much higher significantly than that in other groups (P<0.05). Compared with B2, expression of GFAP in C2 decreased significantly (P<0.05).Conclusions:1. The increase of GFAP expression at convulsion phase and decrease at post-convulsion phase in the hippocampus of penicillin-induced acute seizure rats indicated that astrocyte activation was involved in the process of electric activity of seizure.2. Prolonging the latent period of seizures and decreasing the expression of GFAP in convulsion phase indicated that met al electrodes interfere with the electric activity in the process of epilepticgenesis.