Rossi CA, Lehmkuhle MJ, Dudek FE (2011) Evidence that focal interneuron lesions in the hippocampus may lead to a model of epileptogenesis in the mouse. Neuroscience 2011 Abstracts 249.09. Society for Neuroscience, Washington, DC.
Summary: A selective loss of part of the overall population of GABAergic interneurons is a seminal component of many forms of human epilepsy, and is manifest in many animal models of acquired epilepsy, including those based on chemoconvulsant-induced status epilepticus. The current study specifically tests the hypothesis that partial interneuron loss in the dorsal CA1 area of the hippocampus induces epileptiform activity, and the subsequent hypothesis that interictal-like spikes and seizures progressively worsen during the following weeks and months. Focal interneuron lesions were made by intra-hippocampal injection of SSP-Saporin into dorsal CA1 in the hippocampus of GAD67-GFP transgenic mice. Chronic recording electrodes were implanted at the injection site, and local field potentials (LFPs) were monitored continuously during video recording for several weeks. LFP recordings were analyzed for the occurrence of inter-ictal-like paroxysmal events (hippocampal sharp waves of 50-100 msec), and frank seizures. Although interneuron lesions alone were seen to generate inter-ictal-like activity within several days following surgery, full-blown seizure activity was not observed until several weeks later. The current data suggest that disruption of the local GABAergic interneuron population may be a key event that triggers alteration of neural networks in the hippocampus, leading to paroxysmal events and ultimately seizures. The delay in onset suggests other factors besides interneuron loss play a role in the generation of seizures and the development of epilepsy. Thus, loss of local inhibition may be a necessary, but not sufficient condition for epileptogenesis.
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