J Korean Pediatr Soc.  2000 Jan;43(1):34-42.

The Effect of Erythromycin on Gastric Antrum and Low Esophageal Sphincter in the Newborn Rabbit

Affiliations
  • 1Department of Pediatrics, College of Medicine, The Catholic University, Seoul, Korea.

Abstract

PURPOSE: We studied smooth muscle strips from rabbit gastric antrum and low esophageal sphincter (LES) to explore the difference between newborn and adult rabbit on erythromycin (EM)- induced contractions. Another aim of this study was to determine the mechanism of LES contractile activities induced by erythromycin (EM).
METHODS
Muscle strips prepared from newborn and adult rabbits were stimulated with agonists such as KCl, motilin and EM, and the isometric tensions were measured. To study the underlying mechanism of EM-stimulated contraction of LES, the receptor antagonsts, including tetrodotoxin, hexamethonium, atropine, propranolol and phentholamine, were used. A high concentration of motilin (1 micrometer) was employed to provoke tachyphylaxis.
RESULTS
Antral smooth muscle and LES from newborn rabbits developed less active force than those from adult rabbits when stimulated with KCl, motilin and erythromycin, however, the effective concentrations (EC50s) were similar in both age groups. Antral smooth muscle strips showed both tonic and phasic contractions but LES muscle strips showed only tonic contractions. These findings were observed in both newborn and adult rabbits. The contraction force of antral smooth muscle strips in response to agonists was greater than that of LES. The contractile response of LES to repeated motilin or EM administration was markedly decreased. EM- induced contractions of LES were markedly decreased by motilin tachyphylaxis but were unaffected by tetrodotoxin, hexamethonium, atropine or propranolol plus phentolamine. CONCLUSOIN: The data suggest that the contractilities of antrum and LES smooth muscle from newborn rabbit are less than those from adult ones, however, the effective concentratons of EM (EC50) are not different between the two age groups. The results also suggest that erythromycin induces the contraction of rabbit LES via motilin receptor in vitro.

Keyword

Erythromycin; Motilin; Gastrointestinal motility; Newborn rabbit

MeSH Terms

Adult
Atropine
Erythromycin*
Gastrointestinal Motility
Hexamethonium
Humans
Infant, Newborn*
Motilin
Muscle, Smooth
Phentolamine
Propranolol
Pyloric Antrum*
Rabbits
Tachyphylaxis
Tetrodotoxin
Atropine
Erythromycin
Hexamethonium
Motilin
Phentolamine
Propranolol
Tetrodotoxin
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