The effect of kindling of different nuclei in the left and right amygdala on anxiety in the rat.

The effects on rodent anxiety of kindling in the medial or basolateral amygdaloid nuclei in each hemisphere were examined. Anxiety was measured using the hole board and elevated plus maze tests. The animals were kindled in medial or basolateral amygdalas, of either the left or right hemisphere. Controls had electrodes implanted in comparable areas, but were not kindled. Analysis of electrode location showed that some animals were kindled in amygdaloid nuclei other than medial or basolateral amygdala. These animals were labelled outliers. Kindling of the medial/basolateral amygdala in the left hemisphere decreased anxiety for at least 1 week after the last kindled seizure. Right hemisphere medial/basolateral kindling tended to increase anxiety. Outlier-kindled rats were less anxious than their controls regardless of hemisphere 1 week after their last kindled seizure. Clear anxiogenic effects were not likely seen in the right hemisphere in this study because of the electrode locations. The degree of anxiety following kindling was correlated with electrode location in the anterior-posterior plane. More anterior foci in the amygdala were associated with more anxiety. More posterior amygdala foci were associated with less anxiety. These findings point to the importance of kindled focus in the amygdala for behavioral effect. Future research should carefully control the location of kindled foci when investigating effects of amygdala kindling on anxiety and other behaviors.