THE ACTION OF ADRENALINE, ACETYLCHOLINE AND POTASSIUM IN RELATION TO THE INNERVATION OF THE ISOLATED AURICLE OF THE SPINY DOGFISH (SQUALUS ACANTHIAS)

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Abstract
The isolated sinus-auricle prep. of Squalus acanthias which is apparently without sympathetic innervation, shows marked reactions to adrenaline. The previously reported observation that adrenaline in high conc. causes a transient inhibition was confirmed, but this effect is not blocked by atropine, so it is concluded that the action is not upon the vagus endings as has been suggested, but that it is directly upon the myocardial cells. Adrenaline in low, more nearly physiological concentrations causes augmentation of the contractions without a change in rate. This effect also persists after atropine. The dogfish auricle is much more resistant to the action of acetylcholine in the absence of an inhibitor of choline-esterase than the auricles of frog and turtle hearts, but after treatment with prostigmine the dogfish auricle reacts in the same manner and with approx. the same sensitivity as other vertebrate auricles to acetylcholine. The inhibitory actions of acetylcholine and the depression of auricular beat due to K-excess are markedly antagonized by small concs. of adrenaline. A possible teleological value of the sensitivity of the myocardial cells to adrenaline is suggested.

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