Extrafocal threshold reductions in amygdala-kindled rats. 2010

Brian W Scott, and Harrison Park, and Hua Han, and Ahsanullah Wahidie, and W McIntyre Burnham
Department of Pharmacology and University of Toronto Epilepsy Research Program, University of Toronto, Toronto, Ontario, Canada. mac.burnham@utoronto.ca

OBJECTIVE Racine's classic study suggested that after discharge thresholds were reduced in the primary stimulation site (amygdala) of kindled rats, but that that they were not reduced in secondary (nonstimulated) sites. However, recent reports of neurochemical changes related to excitation and inhibition in nonstimulated sites in kindled brains would be expected to cause reductions in afterdischarge thresholds in these sites. More recently Sanei et al. have reported a significant threshold reduction in the piriform cortex of amygdala- and hippocampus-kindled cats, but not in the entorhinal cortex. The present study was designed to determine whether the results of Sanei et al. in cats could be replicated in rats kindled in the amygdala-a model commonly used in studies of seizure mechanisms and anticonvulsant drug development. METHODS Adult, male Long-Evans rats were kindled in the amygdala or given matched handling. Beginning 48 h following the last stimulation, afterdischarge thresholds were determined in the ipsilateral piriform and entorhinal cortices. Amygdala thresholds were determined 24 h later. RESULTS Afterdischarge thresholds were significantly reduced in both the amygdala and the ipsilateral entorhinal cortex of amygdala-kindled rats. Afterdischarge thresholds in the piriform cortex did not differ significantly between kindled and control subjects. CONCLUSIONS These data suggest that threshold reduction occurs outside the primary kindling site in rats as well as in cats. Extrafocal changes in afterdischarge threshold may be functionally important, and might possibly relate to extrafocal neurochemical changes and progressive generalization of seizure discharge from discrete focal sites.

UI MeSH Term Description Entries
D007696 Kindling, Neurologic The repeated weak excitation of brain structures, that progressively increases sensitivity to the same stimulation. Over time, this can lower the threshold required to trigger seizures. Kindlings, Neurologic,Neurologic Kindling,Neurologic Kindlings
D007839 Functional Laterality Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot. Ambidexterity,Behavioral Laterality,Handedness,Laterality of Motor Control,Mirror Writing,Laterality, Behavioral,Laterality, Functional,Mirror Writings,Motor Control Laterality,Writing, Mirror,Writings, Mirror
D008297 Male Males
D009434 Neural Pathways Neural tracts connecting one part of the nervous system with another. Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, Neural
D009473 Neuronal Plasticity The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations. Brain Plasticity,Plasticity, Neuronal,Axon Pruning,Axonal Pruning,Dendrite Arborization,Dendrite Pruning,Dendritic Arborization,Dendritic Pruning,Dendritic Remodeling,Neural Plasticity,Neurite Pruning,Neuronal Arborization,Neuronal Network Remodeling,Neuronal Pruning,Neuronal Remodeling,Neuroplasticity,Synaptic Plasticity,Synaptic Pruning,Arborization, Dendrite,Arborization, Dendritic,Arborization, Neuronal,Arborizations, Dendrite,Arborizations, Dendritic,Arborizations, Neuronal,Axon Prunings,Axonal Prunings,Brain Plasticities,Dendrite Arborizations,Dendrite Prunings,Dendritic Arborizations,Dendritic Prunings,Dendritic Remodelings,Network Remodeling, Neuronal,Network Remodelings, Neuronal,Neural Plasticities,Neurite Prunings,Neuronal Arborizations,Neuronal Network Remodelings,Neuronal Plasticities,Neuronal Prunings,Neuronal Remodelings,Neuroplasticities,Plasticities, Brain,Plasticities, Neural,Plasticities, Neuronal,Plasticities, Synaptic,Plasticity, Brain,Plasticity, Neural,Plasticity, Synaptic,Pruning, Axon,Pruning, Axonal,Pruning, Dendrite,Pruning, Dendritic,Pruning, Neurite,Pruning, Neuronal,Pruning, Synaptic,Prunings, Axon,Prunings, Axonal,Prunings, Dendrite,Prunings, Dendritic,Prunings, Neurite,Prunings, Neuronal,Prunings, Synaptic,Remodeling, Dendritic,Remodeling, Neuronal,Remodeling, Neuronal Network,Remodelings, Dendritic,Remodelings, Neuronal,Remodelings, Neuronal Network,Synaptic Plasticities,Synaptic Prunings
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D002540 Cerebral Cortex The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulci. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions. Allocortex,Archipallium,Cortex Cerebri,Cortical Plate,Paleocortex,Periallocortex,Allocortices,Archipalliums,Cerebral Cortices,Cortex Cerebrus,Cortex, Cerebral,Cortical Plates,Paleocortices,Periallocortices,Plate, Cortical
D004558 Electric Stimulation Use of electric potential or currents to elicit biological responses. Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004569 Electroencephalography Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain. EEG,Electroencephalogram,Electroencephalograms
D006624 Hippocampus A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation. Ammon Horn,Cornu Ammonis,Hippocampal Formation,Subiculum,Ammon's Horn,Hippocampus Proper,Ammons Horn,Formation, Hippocampal,Formations, Hippocampal,Hippocampal Formations,Hippocampus Propers,Horn, Ammon,Horn, Ammon's,Proper, Hippocampus,Propers, Hippocampus,Subiculums

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