Decreased central histamine in the amygdaloid kindling rats.

This study was conducted to elucidate the role of central histamine (HA) in seizure susceptibility. We stimulated the left amygdala of rats to produce amygdaloid kindling. We sacrificed rats 1 h, 1 week and 1 month after the last kindled seizure, and measured the histamine contents and the histidine decarboxylase (HDC) activities of various brain regions. One hour after the last kindled seizure, we found significant decreases in HA levels in the bilateral amygdala, hippocampus and diencephalon in the kindled group. The HDC activities of the bilateral amygdala and diencephalon were lower in the kindled group than in the control group. One week after the last kindled seizure, we also found a significant decrease in the HA level in the bilateral amygdala. No significant change was found in HA content or HDC activity 1 month after the last kindled seizure. These results suggest that kindling suppresses HA synthesis and that the reduced HA content is maintained until 1 week after the last kindled seizure. The reduced HA may play a role in the acquired kindled seizure susceptibility.