Arousal Reaction in EEG induced by Blood Pressure

IT is supposed by several authors1–9 that adrenaline-induced EEG-arousal, which originates in the mesencephalic reticular formation and the posterior hypothalamus, is caused by a direct action of adrenaline on these structures. Discharges were recorded from single cells within the posterior hypothalamus10,11. The firing-rate of these cells was affected by intravenous injection of adrenaline or by mechanically induced changes of blood pressure. There is no effect of adrenaline if the blood pressure is kept constant artificially. We therefore tested the hypothesis that the adrenaline-induced arousal is a secondary effect of the rising blood pressure.