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

<jats:title>Summary.</jats:title><jats:p>Extracts have been prepared of various kinds of nerves and their content of sympathomimetic activity determined and the actions analyzed.</jats:p><jats:p>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.</jats:p><jats:p>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:</jats:p><jats:p>Blood pressure action on the cat after ergotamine or dihydroergotamine (Fig. 2–4).</jats:p><jats:p>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).</jats:p><jats:p>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).</jats:p><jats:p>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.</jats:p><jats:p>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.</jats:p><jats:p>The possible physiological significance of the solubility of the active substance in ether in the presence of phospho‐lipids is pointed out.</jats:p><jats:p>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.</jats:p><jats:p>Extracts of frogs' hearts contain an active substance with the properties of adrenaline.</jats:p><jats:p>It is suggested that the name sympathin should be used for the ergone demonstrated in adrenergic nerves, exerting the actions of nor‐adrenaline.</jats:p><jats:p>The relationship of the adrenergic ergone to sympathin E and I is discussed.</jats:p>