The alteration of central autonomic excitability and balance induced by noradrenaline and hypotensive drugs (acetylcholine and histamine)

Experiments on lightly anesthetized cats are described in which the autonomic reactivity, tested by the response of the hypothalamus to electrical stimulation, was altered reflexly by the lowering of the blood pressure (induced by acetylcholine, mecholyl or histamine) or by raising the blood pressure with noradrenaline or adrenaline. It was found: The quantitative differences in the degree of autonomic tuning produced by the different procedures are emphasized. The mechanism underlying the experimentally induced alterations in autonomic reactivity, the relation of these states of autonomic imbalance to homeostasis and their clinical and psychological significance are pointed out.