Abstracts

RATIONALE: Compared with unilateral kindling (UK) of the rabbit hippocampus, the simultaneous kindling of bilateral hippocampi (BK: bilateral kindling) was significantly (p[lt]0.01) increased the percentage of animals that successfully kindled while it significantly (p[lt]0.02) decelerated the kindling progression: It was indicated that the BK procedure represents potentiation of both excitatory and inhibitory mechanisms (Kogure et al., Epilepsia, 41(8):929-932, 2000). Recently, alternate-site kindling (AK) of two forebrain structures which induces the phenomenon known as kindling antagonism has been reported (Teskey et al., Epilepsy Res., 34:151-159, 1999). Based on our previous studies of UK and BK, the AK stimulation of the right and left hippocampus was examined to reveal whether it would induce the kindling antagonism or not.
METHODS: Six adult rabbits were used. Under anesthesia, a bipolar electrode was implanted into each side of the hippocaampal CA1 region: These electrodes were used for stimulating as well as recording hippocampal EEGs. The hippocampi were stimulated in alternate sites once every 24h according to Goddard[ssquote]s method (80-160[mu]A, 1ms pulse, 50Hz, 1s application). After completing the kindling, we analyzed the followings: the ratio of kindling achievement, the alterations in behavioral stage and in afterdischarge (AD) duration.
RESULTS: All animals (n=6) developed a stage 5 convulsion with a mean of 30 stimulations (30[plusminus]3: mean[plusminus]S.E.): Accordingly, it was only 15 stimulations that unilateral hippocampus was elicited until the animal was completely kindled. Progressive alterations in behavioral stage were not different between both sides. An averaged alteration of AD duration in AK animals against the number of stimulations was a gradual increment in both sides. Spontaneous occurrences of seizure discharge were not observed.
CONCLUSIONS: In the present study, the perfect generalization in all animals was observed as BK procedure, and not a deceleration but an acceleration in kindling progression was observed like a kindled group (59%) of UK procedure. Therefore, it was concluded that AK was more appropriate model of hippocampal kindling of the rabbits than UK or BK. The reason why the kindling antagonism did not occur in AK procedure is still unknown, regardless of such functions as the feed-back and feed-forward inhibitory systems in the hippocampus.
Support: This work is supported by the Scientific Research Grant in Soka University.