Investigation Of The Effects Of Electrode On Expressions Of MGluR7 And GLT-1 In Penicillin-induced Epileptic Rats

Objective: To understand the mechanisms of the balance between excitation and inhibition in the process of epileptic discharge,the expression of mGluR7 and GLT-1, and the effects of metal electrodes for interfering with their expressions were investigated in each phase of penicillin-induced acute seizure rats by inserting the metal electrodes in rats' epileptic focus.Methods:Acute epileptic models using microinjection in right hippocampus of rats with penicillin, and the metal electrodes were implanted in the foci of injection. 42 Sprague-Dawley rats were divided to 7 groups, including NS control group (A),Pre-convulsions group (B1),Convulsions group (B2),Post-convulsions group (B3),Pre-convulsions with interfering of electrode group (C1),Convulsions with interfering of electrode gorup (C2) and Post-convuslsion with interfering of electrode group (C3) ,and every group includes 6 rats.The animals of the 7 groups will be evaluated in behavior, and the latent period (the time from penicillin injection to epilepsy onset which Racine grade was 2 or above), the frequency of seizures in five minutes at 0h, 1h, 2h and EEG after induced seizure. All the rats were sacrificed at the time point for each group according to requirement and brain tissue was prepared to test the expressions of mGluR7 and GLT-1 by immunohistochemistry.Reasult:1. Comparisons of seizures1.1 The latent periods in groups B1 and B2 were 12.50±4.17 minuts, and the latent periods in groups C2 and C3 were about 17.08±5.50 mintures, which were a little longer than that in B1 and B2 (P<0.05).1.2 In groups B1 to B3, at Oh after epileptic seizure onset, the amplitude of seizures were at Racine Grade 2～3 in most of rats. At 1h after seizure onset, the amplitude of seizure was at Racine Grade 4 in most of rats. At 2h after seizure onset, the amplitude of seizure was at Racine Grade 4～5 in the majority of of rats. In electrodes insertion groups (group C1 to C3), at Oh after epileptic seizure onset, the amplitude of seizures was at Racine Grade 2 in most of rats. At 1h after seizure onset, the amplitude of seizure was at Racine Grade 2～3 in most of rats. At 2h after seizure onset, the amplitude of seizure was at Racine Grade 2～4 in most of rats.1.3 The frequency of seizure was increasing along with time from oh to 3h time points, and it was not interfered by the application of electrodes.2. The changes of EEGThe main EEG waves in NS control group wereα,βwaves, occasionallyθwaves. A series of diverse epilepticform waves were seen on EEG after injection. At 2h after seizure onset, persistent sharp waves, spike waves, sharp and slow wave complexes, with middle and high wave amplitude were showed on EEG mainly, but the frequenies and amplitudes of these waves were decreased in the groups of being interferied with electrodes. At 24h post-seizure onset, low amplitude epileptic waves could still be seen on EEG, although there were no behavioral epileptic seizures.3. Comparisons of the expression of mGluR7 and GTL-13.1 Expressions of mGluR7 in CA3 of hippocampus: compared with group A, mGluR7 expressions were increased signifcantly in groups B1, B2, C1 and C2 (P<0.05); but in groups C3 and B3, the expression had no change (P> 0.05) ; and compared with group B2, the expression in group C2 was decreased signifcantly (P<0.05); and compared with group B1, the expression in Group C1 had a no marked change (P> 0.05) ; and compared with group B3, the expression in Group C3 had a no marked change too (P>0.05) .Expression of mGluR7 in dentate gyrus: compared with group A, mGluR7 expressions in groups B1, B2, C1 and C2 were increased signifcantly (P<0.05); but the expressions were no signifcantly differences between group C1 and B1, and between group C2 and B2 and between group C3 and B3 (P> 0.05) .3.2 Expression of GLT-1 in CA3 of hippocampus: compared with group A, GLT-1 expressions in groups B1,B2,C1 and C2 were increased signifcantly (P<0.05), but in groups C3 and B3, the expression had no change (P> 0.05) ; and compared with group B2, the expression in group C2 were decreased significantly (P<0.05), and compared with group B1, the expression in group C1 had a no marked change (P> 0.05) ; and compared with group B3,the expression in group C3 had a no marked change too (P>0.05) .Expression of GLT-1 in dentate gyrus : compared with group A,GLT-1 expression in groups B1,B2 and C1 were increased significantly (P < 0.05); compared with group B1, the expression in group C1 decreased significantly (P<0.05); but the expressions were no significantly differ- -ences between group C2 and group B2, and between group C3 and group B3 (P> 0.05) .Conclusions:1. The marked changes of mGluR7 and CLT-1 expressions revealed that expressions of mGluR7 and GLT-1 were involved in the process of penicillin-induced seizure.2. mGluR7 and GLT-1 expressions increased at pre-convulsion and convulsion phases, and decreased at post-convulsion phase, meant that the inhibitory barrier was finally broken during the unbalance of excititin and inhibition in seizures.3. The latent period was prolonged by the applocation of electrode during the early phase of preconvulsion, it hinted that shunt of epileptic power was involved in the process of epilepticgenesis.