A STUDY OF THE INNERVATION OF THE PYLORUS OF THE TERRAPIN

¹ From the Department of Physiology, School of Medicine, The Johns Hopkins University, Baltimore

1. A study has been made on the innervation of the excised pylorus of the terrapin (Malaclemmys palustris). The effects of pilocarpine, atropine, epinephrin and ephedrine on the rhythmic contractions and tonus were observed. The action of ephedrine on surviving rings of small intestine was also studied.

2. The rhythmic contractions produced by pilocarpine were slow and powerful. In about half the preparations, the tonus was not affected by pilocarpine; while in the remainder, the tonus was increased. Atropine antagonized the action of pilocarpine, inhibiting the rhythmic contractions and tonus.

3. Epinephrin (adrenalin chloride), in effective doses, inhibited both the tonus and rhythmic contractions, initiated by pilocarpine, in all the preparations except two. In these two sphincters no effect by epinephrin on the rhythm was observed; in one, however, the drug augmented the tonus. Epinephrin, in all effective concentration, had no action on quiescent, relaxed sphincters.

4. Ephedrine hydrochloride, in all concentrations, duplicated the reaction of epinephrin in every experiment. Twice, in the two sphincters mentioned above, ephedrine increased the tonus. On the small intestine ephedrine, like epinephrin, caused inhibition, both of the rhythmic contractions and tonus in all preparations.

5. It is concluded that the splanchnic nerves supply both excitatory and inhibitory motor fibers to the pylorus of the terrapin. The inhibitory fibers predominate, but whenever the excitatory fibers increase in relative numbers they tend to offset the effect of the inhibitory fibers. It is further concluded that ephedrine has a sympathomimetic action.