Abstract
Hoskins and Rawley 1 and Chu and Hsu 2 showed that adrenalin inhibits reflex sympathetic responses in the vascular system. The present study was undertaken to investigate the applicability of these observations to other autonomic reflexes.
In cats under urethane and chloralosane anesthesia the sympathetic nerve to the pupil and nictitating membrane of one eye was separated from the vagus and severed in the neck. Blood pressure and nictitating membranes were recorded by kymograph, and the 2 pupils and a galvanometer indicating the galvanic (sweating) reactions of the foot pads were photographed. Brachial plexus, sciatic and splanchnic nerves were freed, cut, and arranged for stimulation of their central ends. The autonomic responses of the respective pupils and nictitating membranes with and without sympathetic supply, the galvanic (sweating) reactions and blood pressure changes are compared (1) during secretion of adrenine, (2) under the influence of adrenalin perfusion, and (3) after adrenalectomy.
The kymographic and photographic records show that during infusion of adrenalin (1:100,000 to 1:250,000, 1–3 cc/min) sympathetic reflex responses decrease. This is evident from the decreased reflex responses of the normally innervated pupil and nictitating membrane and decreased sweating of the foot pads. The blood pressure is generally slightly elevated and the pressor response to afferent stimuli is reduced. The reflex (inhibitory) dilatation of the sympathectomized pupil is increased. The “damping” effects were generally reduced following ligation of both adrenals. They could be overcome by small injections of metrazol which, according to our previous investigations, 3 greatly accentuates sympathetic responses. In like manner hyperreflexia induced by metrazol could be reduced by injecting adrenalin. The action of adrenin liberated under various conditions in the narcotized animal is similar to that of adrenalin perfusion.
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