Kindling as a neuronal plasticity (Effect of dentate nucleus lesion upon amygdaloid kindling in cats)

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Amygdaloid kindling is used to investigate whether the cerebellar dentate nucleus participate in the neuronal plasticity of the cerebrum in cats. In this study we examined the behavioral change, the occurrence of epileptiform events and duration of afterdischarge during amygdaloid kindling under control conditions and after a contralateral cerebellar dentate lesion in 11 cats. The first stimulation induced stage 2 in five animals out of six in lesioned group, but one of five in control group. The numbers of spikes on the primary site of the amygdala and hippocampus in the lesionde group increased at first, however on the later stage of kindling, those were decreased compared to the control gourp. The spikes on the secondary site of the hippocampus increased more in the lesioned group. Threfore cerebellar dentate lesion facillitated the secondary epileptogenesis. The seizure-related changes of extracellular hippocampal glutamate (Glu) concentration during the development of amygdaloid k … More indling were monitored. The extracellular Glu level enhanced after stimulus and returned rapidly to baseline. In partially kindled rats (stage 3), the extracellular Glu level during the first minutes post stimulus was 2.5-3.5 fold that of the baseline, while fully kindled rats exhibited about a 5-fold increase in the Glu level.Then, we simultaneously monitored the seizure-related changes in extracellular hippocampal glutamate (Glu) and gamma-aminobutyric acid (GABA) concentration in brain dialysates in order to clarify the role of Glu and GABA in the development of kindling. Extracellular GABA concentration gradually, reaching a plateau level at 15-20 min.and lasting for several hours after stimulus at each stage. The enhancement of GABA level was about 1.5 times that of the baseline in the partially kindled stage, and was about 2.5 times of the baseline in the fullly kindled stage. The progressive, transient and stimulus-induced enhancement of extracellular Glu levels combined with long-lasting elevation of extracellular GABA levels in the bilateral ventral hippocampi results in hypersynchrony and imbalance between the excitatory and inhibitory neuronal systems, causing excessive propagation of seizure activity, culminating in the secondary generalized seizure of amygdaloid kindling. Less