Long-lasting depression of hippocampus-mammillary body evoked potentials following stimulation of the basal amygdala in cats

Abstract

Hippocampus-mammillary body evoked potentials were recorded in awake, unrestrained cats. Electrical stimulation of the basal amygdala with intensities eliciting behavioral reactions depressed the amplitude of the evoked responses. This effect, shown in 31 experiments, lasted for 20 min up to more than 4 hr. The induction of epileptic seizures (n = 5) due to amygdaloid stimulation did not modify the duration of this depression. The effect was specific for the basal amygdala, because stimulation of central amygdala and mesencephalic reticular formation did not alter the hippocampus-mammillary body evoked potentials. Lesions within both basal and central amygdala had no constant effect on the hippocampus-mammillary body evoked potentials. The mechanism underlying the suppression of the hippocampus-mammillary body evoked potentials due to electrical stimulation of the basal amygdala is not dependent on paroxysmal activity within hippocampus and mammillary body, as was shown by depth recordings. It is speculated that this mechanism might have a protective function in the propagation of ictal discharges originating within the hippocampus. © 1976.