A FURTHER STUDY OF THE NERVOUS CONTROL OF THE PYLORIC SPHINCTER

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Abstract
The action of epinephrin on the pyloric sphincter in situ and of epinephrin, pilocarpin, atropin, and BaCl2 on the excised pyloric sphincter was studied in dogs, cats, and rabbits. Many of the difficulties that have hitherto attended such studies were obviated by improved methods. The primary action of epinephrin on the sphincter in situ may be to cause either increase or decrease of tonus, the former when the muscle is relaxed, the latter when it is contracted. Increase of tonus in the cat and decrease of tonus in the rabbit were produced but rarely. Rhythmic contractions were generally inhibited. The effects of epinephrin on excised pyloric sphincters, and most commonly on sphincters in situ, were slight contraction followed by more pronounced relaxation in the dog, relaxation in the cat, and contraction in the rabbit. The results with epinephrin are interpreted as indicative of a slight preponderance of inhibitory over motor components in the thoracolumbar sympathetic innervation governing the tonus of the sphincter in the dog and cat and marked preponderance of motor over inhibitory components in the rabbit. Excitatory effects of pilocarpin and the antagonism of atropin for pilocarpin were confirmed on the excised material. BaCl2 caused marked increase of tonus and augmentation of rhythmic contractions.

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