Abstracts

Previously we reported that hippocampal transection attenuated kainic acid (KA)[ndash]induced acute amygdalar seizures. (Akaike et.al, 2001, Imamura et. al., 2001, 2003). The prior studies suggested that such changes of epileptogenicity are related to neurotransmitters, whereas the biochemical mechanism including monoamine changes in this procedure remains obscure. In present study, we investigated the effect of hippocampal transection on KA[ndash]induced acute amygdalar seizures by evaluating intrahippocampal changes of monoamine. Sixteen male Wistar rats were prepared for this study. Stereotactic operation was performed under pentobarbital anesthesia (40 mg / kg i.p.). For microinjection, a stainless steel cannula with an inner needle guide was inserted into the left basolateral nucleus of the amygdala (LA). The rats were also divided into two groups: controls (without transection + KA injection, n=8), TR group (with transection + KA injection, n=8). Hippocampal transection was performed by using [ldquo] Neurotransecter [rdquo]; a flexible arc-shaped blade (diameter, 0.2 mm) made from shape memory alloy placed inside a straight guide cannula (diameter, 0.8 mm). Hippocampal transection was done according to our previous methods (Imamura et al., 2001). On the seventh days after operation, all rats received 1.0mg of KA solution. Two hours after KA injection, animals were decapitated and the ipsilateral hippocampus 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) and 5-hydroxy-indole acetic acid (5-HIAA) then were quantitatively measured using high performance liquid chromatography. Data were analyzed statistically between TR group and controls by using Student[apos]s t-test. Comparing with the dorsal hippocampus, intrahippocampal monoamine in the ventral hippocampus were higher. According to 5-HT and 5-HIAA in TR group were higher in controls, especially in the ventral hippocampus. The rest were unaltered. The effect of hippocampal transection in acute amygdalar seizures is likely to be associated with the changes of 5HT and 5HIAA. (Supported by Grant[ndash]in-Aid for Encouragement of Young Scientists from the Ministry of Education, Sciences, and Culture of Japan.)