Abstracts

We previously stated that hippocampal transection, fiber disconnection between dorsal and ventral hippocampus, attenuated chronic spontaneous amygdalar seizures caused by microinjection of kainic acid into the amygdala (Akaike et.al, 2001, Imamura et. al., 2001, 2003). Though prior studies suggested that such changes of epileptogenicity are likely associated with neurotransmitters, the biochemical mechanism including monoamine changes in this procedure remains veiled. This study was designed to assess the effect by evaluating intrahippocampal changes of monoamine. Experiments were carried out on 18 male Wistar rats having undergone microinjection of kainic acid into the amygdala in advance. More than three weeks later, 12 of them developed with spontaneous amygdalar seizures (Tanaka et al., 1988). They then were divided into three groups ; controls (without spontaneous amygdalar seizures, n=6), SP group (with spontaneous amygdalar seizures, without hippocampal transection, n=6) and SPT group (with spontaneous amygdalar seizures, with hippocampal transection, n=6). Hippocampal transection was done according to our previous methods (Imamura et al., 2001). Under deep anesthesia, animals were decapitated and the hippocampi were removed, then separated to dorsal and ventral portions. Intrahippocampal monoamine including noradrenaline (NA), homovanillic acid (HVA), dopamine (DA), dihydroxyphenyl acetic acid (DOPAC), 5-hydroxytryptamine (5-HT, serotonin) and 5-hydroxy-indole acetic acid (5-HIAA) then were quantitatively measured using high performance liquid chromatography and statistical analysis was carried out. Comparing with controls, NA in dorsal hippocampus and DA and DOPAC in ventral hippocampus were lower and 5-HT and 5-HIAA in dorsal and ventral hippocampi were higher in SP group. The rest were unaltered. In SPT group, after hippocampal transection was performed, DA and DOPAC in ventral hippocampus increased again, while NA in dorsal hippocampus and 5-HT and HIAA in dorsal and ventral hippocampi remained unchanged. The biochemical mechanism of hippocampal transection in spontaneous amygdalar seizures is likely to be associated with the changes of DA and DOPAC in ventral hippocampus. (Supported by Grant[ndash]in-Aid for Encouragement of Young Scientists from the Ministry of Education, Sciences, and Culture of Japan.)