Characterization of the defensive nature of kindling-induced emotionality.

Long-term amygdala kindling produces substantial changes in emotional behavior in rats. The purpose of these experiments was to determine whether kindling-induced emotionality is fundamentally defensive or aggressive in nature. In Experiment 1, amygdala-kindled rats tested as intruders in a resident-intruder paradigm preferred an active defense strategy (i.e., defensive upright stance, jump attacks), whereas the sham-stimulated rats preferred a passive defense strategy (i.e., freezing). In Experiment 2, amygdala-kindled rats explored an unfamiliar open field significantly less than did the sham-stimulated rats, and they were significantly more resistant to capture from the unfamiliar open field than were the sham-stimulated rats. In contrast, there were no significant differences between the kindled and sham-stimulated rats in resistance to capture from their home cages. These results suggest that the emotionality produced by long-term amygdala kindling is fundamentally defensive in nature.