Neuronal microdysgenesis and acquired lesions of the hippocampal formation connected with seizure activities in Ihara epileptic rat.
The present study was designed to examine the morphological features of the hippocampal formation in the Ihara epileptic rat (IER), and to characterize genetically programmed lesions and acquired lesions connected with seizure activities. Neuropathological investigation of the hippocampal formation was performed in four separate groups, 2-month-old IERs with neither abnormal behaviors nor any seizure activity, and 12-month-old IERs of both sexes with abnormal behaviors, circling seizures or generalized tonic-clonic convulsions. In every IER examined, there were invariable and fundamental neuropathological findings consisting of abnormal neuronal clusters in the CA1 of the hippocampal formation. Moreover, disarrangement of neuronal cells, such as dispersion and gaps in lamination of pyramidal neurons, were observed. These changes were thought to represent genetically programmed lesions, neuronal microdysgenesis, because they were common findings in 2-month-old and 12-month-old IERs of both sexes. An enlargement of the dentate gyrus was also found in rats that experienced generalized tonic-clonic convulsions or circling seizures. This enlargement of the dentate gyrus, on the other hand, was categorized as a secondary and acquired lesion connected with seizure activities. It is suggested that the neuronal microdysgenesis in the hippocampal formation of IER has an intimate relationship with epileptogenesis and/or an enhancement of seizure susceptibility.
Tsuji
A
A
Department of Neurosurgery, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu, Japan. atushi@belle.shiga-med.ac.jp
Amano
S
S
Yokoyama
M
M
Fukuoka
J
J
Hayase
Y
Y
Matsuda
M
M
D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D018891:Dentate Gyrus / Q000002:abnormalities / Q000473:pathology / Q000503:physiopathology; D004827:Epilepsy / Q000151:congenital* / Q000235:genetics / Q000473:pathology; D005260:Female; D006624:Hippocampus / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D009474:Neurons / Q000473:pathology*; D051381:Rats; D011922:Rats, Mutant Strains / Q000002:abnormalities* / Q000235:genetics; D012640:Seizures / Q000151:congenital* / Q000235:genetics / Q000473:pathology