Abstracts

The EL mouse is an inbred mutant strain that is used as an animal model of secondarily generalized seizures. Epileptogenesis in EL mice is thought to be caused by collapse of redox state induced by either decreased antioxidant protection or excessive free radical formation. However, measurement of reductants in brain tissue extracts is problematic because synergistic actions of antioxidants such as ascorbic acid, alpha tocopherol or glutathione are effective in scavenging free radicals. Using in vivo methods we developed, we evaluated hippocampal antioxidant ability in EL mice with X-band Electron Paramagnetic Resonance (EPR) spectroscopy and microdialysis., Using sodium pentobarbital anesthesia, each mouse underwent stereotactic implantation of guide cannula into the ventral hippocampus. EL mice were injected i.p. with the nitroxide radical 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCAM) at 677 micromol/kg (3.3 ml saline/kg). Following PCAM injection sequential measurements with EPR were used to monitor levels of nitroxide radicals in the extracellular fluid of the hippocampus. In vivo antioxidant efficacy was estimated based on the principle that PCAM loses paramagnetism and that the decay rate of the EPR signal expressed as half life will reflect tissue antioxidant efficacy. Animals used included experimental groups of 6 five week old and 6 eight week old EL mice; all animals were interictal. Mice from the originating strain of EL mice, DDY mice of similar age, were used as controls., EPR half-life in the five week old mice was equal to control. However, by eight weeks there was significant prolongation in EPR half-life in EL mice when compared to both control groups of DDY mice. None of the EL mice used in this experiment were subjected to seizure-inducing stimulation and they remained in the interictal state., Since five week EL mice do not seize in response to tossing stimulus while by eight weeks EL mice are subject to seizures, we concluded that the decreased in vivo antioxidant ability is a fundamental change related to development of seizures., (Supported by Grant-in-Aid for Scientific Research (C) (2) (18591297) from the Ministry of Education, Science, Sport and Culture, Japan (to Y.U.).)