Abstract: To study a role of dynorphin A(1-8)(DYN A(1-8))in ventral hippocampus during induction of enhanced seizure susceptibility, an acute model as human temporal lobe epilepsy was made by kainic acid(KA)causing seizure episode in the rats. The time course of alteration of dynorphin A(1-8)like immunoreactivity in ventral hippocampus during induction of enhanced seizure susceptibility(1～7 d after KA)was detected by immunocytochamical method. SD rats were given 10 mg/kg,S.C. of KA systemically. Two days later, dynorphin A(1-8)immunoreactive neurons appeared in the nuclei of dentate granule cells(DGC)in ventral hippocampus. The maximal intensity of staining and the largest number of the immunoreactive dynorphin A(1-8)occurred 4 d after KA. Five to seven days after KA, during induction of enhanced seizure susceptibility, dynorphin A(1-8)immunoreactive neurons also gradually disappeared in DGC of ventral hippocampus. Endogenous dynorphin in the seizure sensitive ventral hippocampus appeares to play an important role in regulation of brain excitability, especially in the induction of enhanced seizure susceptibility.

Key words: seizure susceptibility, ventral hippocampus, kainic acid, dynorphin A(1-8)