ON THE MECHANISM OF FREQUENCY GRADIENT OF RHYTHMIC CONTRACTIONS IN THE SMALL INTESTINE OF DOGS

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1) The experiments were performed to study the relationship between frequency gradient and the myenteric nervous activity. 2) The segments of upper jejunum andlower ileum of decerebrated dogs anesthetized with chloralose were perfused under a constant pressure between 3 to 16 cmH2O. The rhythmic contraction of the segments were recorded by means of strain-gauge pressure transducer. 3) The mean frequencies of rhythmic contractions ranged, between dogs, from 11.5 to 17.3 cycles/min in jejunal segment and from 8.0 to 13.5 cycles/min in ideal segment, and so definite frequency difference between them was evident in the same specimen. 4) The frequencies of contractions of jejunal and ileal segments were uninfluenced by the section of cervical vagi or thoracic splanchnic nerves. They were markedly reduced after administration of procaine or hexamethonium bromide. With or without pretreatment of tetrodotoxin they were increased by administering carbamylcholine, while those activated with morphine were reduced by application of atropine or tetrodotoxin. In all of the cases mentioned above, the frequency gradient was still evident. 5) It may be concluded that the function concerned with the frequency gradient is the muscle responsibility to the intrinsic nervous influences and that the frequency of contractions in each segment is largely corresponded to the intrinsic nervous activity.
日本平滑筋学会の論文