Changes in excitability of amygdaloid and septal nuclei induced by medazepam hydrochloride

Electrical stimulations of the central and basolateral part of the amygdaloid complex and of the septum in freely moving cats elicit changes in arterial pressure (i.e., an increase in pressure during stimulation of the central part of the amygdala, and a decrease followed by an increase during stimulation of the basolateral part of the amygdala and of the septum). These changes within the cardiovascular system are followed by rage reactions when the central part of the amygdala is stimulated, defense patterns when the basolateral part of the amygdala is stimulated, and pitiful mewing as a result of septal stimulation. Medazepam hydrochloride in a dose of approximately 15 mg/kg i.v. given over a period of 3 h, in order to maintain constant blood levels of the drug, attenuated slightly the cardiovascular reactions and elevated markedly the thresholds for psychomotoric behavior. The latencies between the onset of electrical stimulation and the beginning of the increase in arterial pressure were only slightly increased, whereas the latencies for spychomotoric behavior were markedly prolonged due to drug application. The data support the view that medazepam hydrochloride exerts depressant effects on the limbic-hypothalamic level with respect to psychomotoric responses. The effect was not identical for all nuclei tested. The basolateral part of the amygdala was significantly less sensitive to medazepam hydrochloride than the central part of the amygdala.