Rodent anxiety and kindling of the central amygdala and nucleus basalis

We studied lasting behavioral effects of kindling of three parts of the central nucleus of the amygdala and the anterior nucleus basalis in the right hemisphere of male Wistar rats. Kindling lastingly changed two measures of anxiety in the elevated plus-maze. The nature of the change depended on the location of the kindled focus. Kindling of the posterior central nucleus decreased both open-arm exploration and frequency of risk assessment in the elevated plus-maze 1 week after the fourth stage 5 seizure. Kindling of the middle parts of the central nucleus was without behavioral effects. Kindling of the anterior central nucleus and the anterior nucleus basalis increased risk assessment, which was interpreted as an anxiolytic effect. Changes in risk assessment produced by kindling of the central nucleus were dependent on open-arm avoidance, whereas the effects of nucleus basalis kindling were independent of open-arm avoidance. Analysis of covariance and factor analysis support the view that control of risk assessment is by circuitry, which is independent of that which controls open-arm avoidance. Moreover, part of this circuitry appears to involve the anterior nucleus basalis. Changes in plus-maze behavior were independent of changes in exploration or activity in either the plus-maze or hole board. These findings add to a growing body of evidence that suggests that subtle differences in location of a kindled focus within the rat amygdala lead to different behavioral outcomes. (C) 2000 Elsevier Science Inc. All rights reserved.