EFFECT OF ADRENALINE ON THE HYPOTHALAMIC ACTIVATING SYSTEM

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Abstract
Using cats immobilized by Flaxedil, the effect of adrenaline and noradrenaline on electrical activity of the neo-, paleo-, and archicortical systems was studied. In the anterior mesencephalon transected cat, intracarotid injection of adrenaline and noradrenaline (5-10/[mu]g/kg) elicited an arousal pattern in the amygdala and hippocampus, while the neocortical area and caudate nucleus showed a sustained sleep pattern. However the change in blood pressure and in the cerebral vessels had no direct relation to the activation of electrical activity of the brain. In the anterior mesencephalon transected cat a bilateral electrolytic lesion of the posterior hypothalamus abolished activation of the limbic system in response to intracarotid injection of adrenaline and noradrenaline. In a preparation with massive lesions of the posterior hypothalamus, the activation pattern in the paleo, and archicortical systems could bot not be produced by adrenaline, although the neocortical electrical activity occasionally showed a transient change. Adrenaline or noradrenaline evidently act not on the midbrain reticular formation but primarily on the hypothalamus.