Unilateral Low-frequency Stimulation Of Central Piriform Cortex Delays Seizure Development Induced By Amygdaloid Kindling In Rats

1. Unilateral low-frequency stimulation of central piriform cortex delays seizure development induced by amygdaloid kindling in ratsLow-frequency stimulation (LFS) of the kindling site interferes with the course of kindling epileptogenesis. The present study examined the effect of unilateral LFS of the central piriform cortex (cPC) on seizure development induced by amygdaloid kindling in rats. The ipsilateral or contralateral cPC received LFS (15 min train of 0.1 ms pulses at 1 Hz and 50-150 μA) immediately after termination of once daily kindling stimulation (2 s train of 1 ms pulses at 60 Hz and 150-300 μA) in the right amygdala for 30 days. LFS of either the ipsilateral or contralateral cPC significantly suppressed theprogression of seizure stages and reduced afterdischarge duration throughout the course of amygdaloid kindling. The marked suppression induced by LFS of the cPC on either side were both predominantly due to the significant retardation of progression from stage 0 to stage 1 and stage 3 to stage 4 seizures. In addition, the suppressive effect of LFS did not disappear when the stimulation was stopped;it could persist for at least 10 days. These findings indicate that brain areas other than the kindling focus, such as the cPC on both sides, can also be used as reasonable targets for LFS to retard seizure development induced by amygdaloid kindling. Secondly, like the ipsilateral cPC, the contralateral cPC may also participate in the progression and secondary generalization of focal seizures. The study suggests that unilateral LFS of the cPC may have a significant antiepileptogenic effect, and may be helpful for the exploring on effective and long-lasting therapies for human temporal lobe epilepsy.2. The anticonvulsant effect of unilateral microinjection of saline into the central piriform cortex of amygdaloid-kindled ratsThe central piriform cortex (cPC) is thought to be critically involved in the generation and propagation of limbic seizures in the rats. In the present study, we investigate the effect of different volume of saline unilateral microinject into the cPC on the generalized seizure threshold and seizure duration in kindled rats. We microinjectedthree volumes (0.1, 0.25 and 1 \i\) of saline into the right or left cPC of previously amygdaloid-kindled rats and repeatedly test its effect on kindled seizure. We found that three volumes of saline in all groups not only increased the generalized seizure threshold of seizure but also decreased the seizure duration. And this anticonvulsant effect was for up to 10 days with a maximal effect 4 days after injection. However, the anticonvulsant effect of saline on seizure generalization was volume-dependent. From this data, we can conclude that (1) unilateral microinjection saline into the cPC can inhibit the generalization seizure volume-dependently;(2) These findings also indicate that not only ipsilateral cPC but also contralateral cPC were involved in the generalized seizure. The study suggests that unilateral microinjection saline into cPC may have a significant anticonvulsant effect and may be used as an effective and long-lasting therapy for human temporal lobe epilepsy in the future.