HYPEREXCITABILITY - EXAGGERATED FEAR-POTENTIATED STARTLE PRODUCED BY PARTIAL AMYGDALA KINDLING

The present study asked whether partial amygdala kindling would affect the expression of conditioned fear-potentiated startle. Rats were con ditioned to be fearful of a light. They were then stimulated bilateral ly in the amygdala or hippocampus on 2 consecutive days (partial kindl ing). Rats were tested 24 hr later for fear-potentiated startle. Amygd ala-kindled rats had exaggerated fear-potentiated startle compared to sham-kindled rats. Hippocampus-kindled rats also displayed fear-potent iated startle, but no greater than that of sham-kindled rats. Partial amygdala kindling induced c-fos messenger RNA (mRNA) expression, a mar ker for neuronal activation, throughout the limbic and neocortices. In contrast, partial hippocampus kindling induced c-fos mRNA in the hipp ocampus only. The data suggest that kindled-induced hyperexcitability of the amygdala and limbic cortices produced exaggerated conditioned f ear-potentiated startle.