Open‐field Behaviors and Water‐maze Learning in the F Substrain of Ihara Epileptic Rats

Abstract

Summary:Purpose: Genetically epileptic model rats, Ihara epileptic rat (IER/F substrain), have neuropathologic abnormalities and develop generalized convulsive seizures when they reach the age of ∼5 months. Because the neuromorphologic abnormalities are centered in the hippocampus, we expected to observe spatial cognitive deficits. The present study aimed to evaluate emotionality and learning ability of the F substrain of IER.Methods: To determine whether deficits are caused by inborn neuropathologic abnormalities or by repeated generalized convulsions, we tested nine 6-to 12-week-old IER/F rats that had not yet experienced seizures (experiment 1) and nine 7-to 9-month-old IER/F rats that had repeatedly experienced seizures (experiment 2) with identical tasks: an open-field test and the Morris water-maze place and cue tasks.Results: Both groups of IER/Fs showed behaviors that were different from those of control rats in the open-field test, and extensive learning impairments were seen in both the place task, which requires spatial cognition, and the cue task, which does not require spatial cognition but requires simple association learning. Their impaired performance of the cue task indicates that their deficiency was not limited to spatial cognition.Conclusions: Because young IER/F rats without seizure experiences also showed severe learning impairments, genetically programmed microdysgenesis in the hippocampus was suspected as a cause of the severe learning deficits of IER/Fs.

The Electromagnetic Field Changes on Emotional-motivated Behavior in Genetically Epilepsy-prone Rats

“…More specifically, increases in the number of crossed squares, vertical stands, entering the center and the duration of the time spent in the center are the signs of increased locomotor activity and decreased fear (5,13) . Grooming is an important and evolutionarily ancient behavior.…”

Down syndrome cell adhesion molecule like-1 (DSCAML1) links the GABA system and seizure susceptibility

“…The frequency and the degree of seizures increase with aging (Additional file 1: Video 1) [3,4] Neuropathological investigation revealed that IERs exhibit small neuronal disarrangements consisting of irregular arrangements of pyramidal cells, gap formation in the array of the pyramidal cell layer, and abnormal tiny loci of neuronal clusters in the hippocampal formation (i.e., microdysgenesis; MDG) [5]. In addition, IERs exhibit behavioral impairment in social interaction, controlling emotions and spatial learning even before the onset of any seizure-related behaviors [6]. Similarly, some cases of human epilepsy are often accompanied by such psychiatric symptoms.…”

Acoustic Range Electric-Magnetic Field Exposure Decreases Cortical Excitability in Genetically Epilepsy-Prone Rats

“…Despite the fact that it is possible to treat epilepsy using pharmacological substances, about 30-40% of the patients are resistant to such treatment (WHO, media Center 2016). In addition, a long-term consumption of the drugs negatively affects the patients' cognitive functions [1][2][3]. The effectiveness of pharmacological agents, used for epilepsy treatment is limited due to incomplete understanding of the mechanisms involved in the pathogenesis of the disease.…”