A Specific Sympathomimetic Ergone in Adrenergic Nerve Fibres (Sympathin) and its Relations to Adrenaline and Nor‐Adrenaline

Abstract

Summary.: Extracts have been prepared of various kinds of nerves and their content of sympathomimetic activity determined and the actions analyzed. The thoracic and lumbar sympathetic chain and the splenic periarterial nerves were especially suitable for preparation of the active substance and contained some 30–100 μg adrenaline equivalents per g as measured on the blood pressure of the cat. The active substance gives catechol reactions and bears near relations to adrenaline, but differs characteristically from this in the following respects, where a close resemblance to nor‐adrenaline was found: Blood pressure action on the cat after ergotamine or dihydroergotamine (Fig. 2–4). Action on non‐pregnant cat's uterus (Fig. 5 A), pregnant rabbit's uterus (Fig. 6) and the isolated intestine of the cat and rabbit (Fig. 7). Pupil‐dilating action (Fig. 8). Fluorescence test. The active substance occurs in higher amounts in the grey sympathetic rami than in the white rami (Fig. 10). The content is fairly high in sensory nerves of the skin but low in sympathetic ganglia, the vagus and phrenic nerves and various parts of the brain. After degeneration of the main portion of the (post‐ganglionic) periarterial splenic nerves the content of the spleen of the active substance is greatly reduced. The possible physiological significance of the solubility of the active substance in ether in the presence of phospho‐lipids is pointed out. From the experiments it is inferred that the active substance is the physiological transmitter of adrenergic nerve action in mammals and identical with nor‐adrenaline. Extracts of frogs' hearts contain an active substance with the properties of adrenaline. It is suggested that the name sympathin should be used for the ergone demonstrated in adrenergic nerves, exerting the actions of nor‐adrenaline. The relationship of the adrenergic ergone to sympathin E and I is discussed.