Responses of human clasp and sling fibers to neuromimetics.
OBJECTIVE
It has previously been demonstrated that clasp and sling fibers at the human gastroesophageal junction respond differently to acetylcholine (Ach). The present study was undertaken to investigate the differences between the physiological and pharmacological properties of the two types of muscle fiber.


METHODS
Recordings were made of the isometric tension of human sling and clasp fibers in response to Ach, dopamine (DA), phenylephrine (Phe), and isoprenaline (Iso). These specimens were obtained from 18 patients who were operated on for esophageal cancer.


RESULTS
Both Ach and Phe increased the tension of the two types of muscle; the values in the Ach group being 3-4-fold greater than those in the Phe group, while Iso decreased the tension of both types of muscle strip. The tension of the sling fibers was reduced by DA at lower concentration, and then increased gradually as the concentration was increased. In contrast, the tension of the clasp fibers did not obviously change when the concentration of DA was lower, but a slow elevation of tension was seen with the increase in DA concentration.


CONCLUSIONS
The sensitivities and maximum responses to each agent differed between the clasp fibers and sling fibers. This suggests that the two kinds of fiber have different roles in establishing tension in the lower esophageal sphincter, with implications for the medical and surgical treatment of disorders in this region.
Tian
Zi-Qiang
ZQ
Department of Thoracic Surgery, Fourth Hospital, Hebei Medical University, Shijiazhuang, China. tizq12@heinfo.net
Liu
Jun-Feng
JF
Wang
Gui-Ying
GY
Li
Bao-Qing
BQ
Wang
Fu-Shun
FS
Wang
Qi-Zhang
QZ
Cao
Fu-Min
FM
Zhang
Yue-Feng
YF
D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D018678:Cholinergic Agents / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000503:physiopathology; D004943:Esophagogastric Junction / Q000187:drug effects* / Q000503:physiopathology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology*
D018678:Cholinergic Agents; D013566:Sympathomimetics; D010656:Phenylephrine; D007545:Isoproterenol; D000109:Acetylcholine; D004298:Dopamine