Hippocampal cell loss and propagation of abnormal discharges accompanied with the expression of tonic convulsion in the spontaneously epileptic rat.
Spontaneously epileptic rats (SER) are double mutants with both tonic convulsion and absence-like seizures from the age of 8 weeks. Hippocampal CA3 neurons in SER display a long-lasting depolarizing shift accompanied by repetitive firing (attributed to abnormalities of the Ca(2+) channels) with a single stimulation of the mossy fibers. In the present investigation, we examined if the seizure discharges of SER were correlated with the hippocampal abnormality of SER using electrophysiological and histological methods. In CA1 neurons of seizure-susceptible mature SER, higher-voltage (<8-11 V) stimulations induced a long depolarization shift (in 25% of neurons) with repetitive firing (in 12.5% of neurons). However, the tremor rat, one of the parent strains of SER, did not exhibit such abnormal firing in the CA3 region of the hippocampus. The number of CA3 neurons in SER was significantly (p<0.01) lower than that in tremor rats and Wistar rats, although no significant difference was established in the hilus. Sprouting of mossy fiber was observed in the dentate of mature SER; however, negligible staining was spotted in the dentate of both mature tremor and Wistar rats. Interestingly, expression of the brain-derived neurotrophic factor was higher in the hilus, CA3, and granular cell layer of dentate gyrus in SER than normal Wistar rats. The expression levels of TUNEL, bax, and Caspase-3 did not show significant changes between the SER and Wistar rats. SER exhibited hippocampal sclerosis-like changes which did not have enough potential for epileptogenesis. Repetitive tonic seizures and vulnerable CA3 neurons of SER could be involved in the induction of sclerosis-like changes in the hippocampus.
Hanaya
Ryosuke
R
Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan. hanaya@m2.kufm.kagoshima-u.ac.jp
Sasa
Masashi
M
Sugata
Sei
S
Tokudome
Mai
M
Serikawa
Tadao
T
Kurisu
Kaoru
K
Arita
Kazunori
K
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D056547:CA1 Region, Hippocampal / Q000473:pathology / Q000503:physiopathology; D056654:CA3 Region, Hippocampal / Q000473:pathology / Q000503:physiopathology; D016923:Cell Death; D018891:Dentate Gyrus / Q000166:cytology / Q000502:physiology; D004195:Disease Models, Animal; D004827:Epilepsy / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D019599:Mossy Fibers, Hippocampal / Q000502:physiology / Q000648:ultrastructure; D009410:Nerve Degeneration / Q000473:pathology* / Q000503:physiopathology*; D009474:Neurons / Q000473:pathology / Q000502:physiology; D009924:Organ Culture Techniques; D051381:Rats; D011922:Rats, Mutant Strains; D017208:Rats, Wistar; D012598:Sclerosis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D012640:Seizures / Q000235:genetics / Q000473:pathology / Q000503:physiopathology
D019208:Brain-Derived Neurotrophic Factor