Open-field behaviors and water-maze learning in the F substrain of Ihara epileptic rats.
OBJECTIVE
Genetically epileptic model rats, Ihara epileptic rat (IER/F substrain), have neuropathologic abnormalities and develop generalized convulsive seizures when they reach the age of approximately 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.
Okaichi
Yoko
Y
Department of Psychology, Doshisha University, Kyoto, Japan. yokaichi@vesta.dti.ne.jp
Amano
Shigeru
S
Ihara
Nobuo
N
Hayase
Yoneko
Y
Tazumi
Tooru
T
Okaichi
Hiroshige
H
D000367:Age Factors; D000818:Animals; D001245:Association Learning / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D004195:Disease Models, Animal; D004827:Epilepsy / Q000523:psychology; D004833:Epilepsy, Temporal Lobe / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D004924:Escape Reaction / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology; D006624:Hippocampus / Q000002:abnormalities / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007696:Kindling, Neurologic / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D009043:Motor Activity / Q000235:genetics*; D010554:Personality Disorders / Q000523:psychology; D017966:Pyramidal Cells / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D011922:Rats, Mutant Strains; D017208:Rats, Wistar; D012640:Seizures / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*; D013647:Task Performance and Analysis