Effect of transient hippocampal inhibition on amygdaloid kindled seizures and arnygdaloid kindling rate

In this study the effect of transient inhibition of the CAI region of the dorsal hippocampus by lidocaine on amygdala kindling rate and amygdaloid kindled seizures was investigated. In experiment 1, rats were divided into four groups. In group 1, animals were implanted only with a tripolar electrode into the amygdala but in groups 2-4, two guide cannulae were also implanted into the CAI regions of the dorsal hippocampi. Animals were stimulated daily to be kindled. In groups 3 and 4, saline or 2% lidocaine (1 mul/2 min) was also injected respectively into the hippocampus, 5 min before each stimulation. Results obtained showed that amygdala kindling rate and the number of stimulations to receive from stage 4 to stage 5 seizure were significantly increased in group 4, In experiment 2, lidocaine (1% and 2%) was infused (I mul/2 min) into the hippocampus of amygdala kindled rats bilaterally and animals were stimulated at 5, 15 and 30 min after drug injection. Twenty four h before lidocaine injection, saline was also infused (1 mul/2 min) into the hippocampus as control. Obtained results showed that afterdischarge duration was reduced 5 min after lidocaine (1% and 2%) injection. Stage 5 seizure duration was also decreased 5 and 15 min after 2% lidocaine. Thus, it may be suggested that in amygdala kindling, activation of the hippocampal CAI region has a role in seizure acquisition and seizure severity so that inhibition of this region results in decreasing of seizure severity and retards amygdala kindling rate. (C) 2002 Elsevier Science B.V. All rights reserved.