Electrical brain activity and cardiovascular function during amygdaloid kindling in the dog

Two lines of evidence converged to suggest that amygdaloid kindling would produce alterations in cardiovascular responsiveness. First, stimulation of the amygdala produces changes in heart rate and blood pressure. Second, the amygdala is the most sensitive region of the brain for kindling. Our objectives were to document the electrical brain activity, cardiovascular responses, and behavioral manifestations associated with the development of generalized convulsions during amygdaloid kindling in the dog. Kindling in the dog was marked by its rapidity and lack of graded stages, resulting in two identifiable stages. The first, afterdischarge stage, was characterized by increased electrical brain activity in the stimulated amygdala but not in the ipsilateral anterior or posterior hypothalamus, or contralateral amygdala. Increased blood pressure was closely related to the activity of the stimulated amygdala, and a gradual increase in heart rate was unrelated to activity at any of the recording sites. Behavioral manifestations were confined to head and neck movements. The second, convulsion stage, was typified by increased activity in both amygdalae and in the anterior hypothalamic recording sites, indicating generalized involvement of both hemispheres. Blood pressure was significantly increased consistent with the behavioral manifestations of bilateral tonic-clonic convulsion. Heart rate during the convulsion was not significantly different from that during the afterdischarge stage. This experiment, therefore, demonstrated that kindling in the dog follows a substantially different progression from that reported in other species and that kindled afterdischarges in the amygdala had a potent effect on blood pressure, even in the absence of generalized convulsions.