Study On Contents Of Extracellular Amino Acid Of Hippocampus In Rat With Seizure And The Neuroprotective Effect Of Topiramate On Seizure Rats

1. Objective:To examine the amino acid levels in rat hippocampus at multiple time points after PTZ-induced seizures. To detect neuronal apoptosis in rat hippocampus after PTZ-induced seizures. To investigate the effects of intervention of TPM and to explore a new therapy for epileptic bra n damage.2.Methods:A status epilepticus model was established by intra-peritoneal injection of PTZof rats.(1) Male adult Sprague-Dawley rats (180~250g) were used in this seizure model. The extracellular amino acid neurotransmission was measured by in vivo microdialysis with HPLC before and after PTZ administration.(2) After status epilepticus induced by PTZ administration in male adult rats, we treated the rats with topiramate (TPM) at 80mg/kg/d or Cabamazipine at 40mg/kg/d for 2 weeks. Programmed cell death (Apoptosis) was identified by terminal deoxynucletidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) assay to detect DNA fragmentation. The extracellular amino acid neurotransmission levels in hippocampus of free-moving rats were detected by microdialysis with HPLC.3. Results:(1) The extracellular GAB A concentration in the CA1 area decreased immediately after the administration of PTZ but increased at about 3d after PTZ injection and lasted about 2 weeks. However, Glu level increased remarkably after the PTZ injection and decreased at 3d until 14d after PTZ injection.(2) Two weeks following seizures, TUNEL-positive neurons were detected in CA1, CA3 subfields in each group. The number of TUNEL-positive neurons in CA1 and CA3 of control group were 35.83 + 4.58, 36.83 + 3.83 respectively; Those of TPM group were 21.17 + 3.06, 21.16 + 3.87 respectively and of Cabamazipine group were 23.50 + 2.81, 25.50+3.72 respectively. Administration of topiramate significantly reduced hippocampal neuronal damage. However, no differences in histological study of TUNEL-positive neurons between TPM and cabamazipine groups was found.(3) TPM significantly reduced glutamate level but elevated GABA levels in the hippocampus of seizure rats.4. Conclusions:(1) The changes of GABA and Glu level were strongly related to the epileptic seizure and seizure-induced neuronal injury. The results suggested that an imbalance between excitatory and inhibitory neuronal systems plays acritical role in the mechanism of seizure and seizure-induced brain damage.(2) Administration of TPM after experimental status epilepticus can attenuate seizure-induced hippocampal neuronal injury. This effect may, at least in part, be related to the changes of amino acid. However, there was no difference between TPM and Cabamazipine histologically.