Developmental changes in agonist-mediated gastric smooth muscle contraction in the rabbit

ABSTRACT ABSTRACT: We studied smooth muscle strips from rabbit proximal stomach to explore the age-related changes in agonist-mediated contraction. Strips from neonatal (1 d) and weanling

(11 wk) rabbits were oriented to measure isometric tension in circular muscle. Bethanechol stimulated maximal tension in both age groups. Although the potencies for bethanechol were similar

(ED50 ∼5 μM), the maximal response was nearly 4-fold greater in weanling (1140 ± 73 mN/cm2) _versus_ neonate (305 ± 54 mN/cm2), _p_ < 0.001. Maximum stress increased with age for

bethanechol, high extracellular K+, and substance P, but not for serotonin, cholecystokinin octapeptide, neurotensin, or bombesin. Only bombesin stimulated larger contraction in neonates

(152 ± 37 mN/cm2) _versus_ weanlings (86 ± 20 mN/cm2), _p_ < 0.05. Potencies did not change with age, except for substance P and serotonin. Substance P and serotonin induced early phasic

and prolonged tonic contractions, which were unaffected by tetrodotoxin or atropine. ED50 for the phasic and tonic components of substance P-stimulated contraction in neonates were 1.8 and

7.7 nM. Substance P was 60-70 times more potent in neonates _versus_ weanlings (_p_ < 0.001). ED_50_ for serotoninstimulated contraction in neonates (33 and 22 nM, respectively) were

20-30 times more potent than in weanlings (_p_ < 0.05). Motilin, morphine, epidermal growth factor, and gastrin did not stimulate contraction at either age. We conclude that age-dependent

changes in agonist potency and efficacy may be one factor to explain in part the changes that occur in gastric motility during postnatal development. SIMILAR CONTENT BEING VIEWED BY OTHERS

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Department of Pediatrics and Medicine and the Inflammatory Bowel Disease Center, Harbor-UCLA Medical Center, Torrance, 90509, California Takeshi Tomomasa, Hideki Yagi, Saburo Kimura, William

J Snape JR & Paul E Hyman Authors * Takeshi Tomomasa View author publications You can also search for this author inPubMed Google Scholar * Hideki Yagi View author publications You can

also search for this author inPubMed Google Scholar * Saburo Kimura View author publications You can also search for this author inPubMed Google Scholar * William J Snape JR View author

publications You can also search for this author inPubMed Google Scholar * Paul E Hyman View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND

PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Tomomasa, T., Yagi, H., Kimura, S. _et al._ Developmental Changes in Agonist-Mediated Gastric Smooth Muscle

Contraction in the Rabbit. _Pediatr Res_ 26, 458–461 (1989). https://doi.org/10.1203/00006450-198911000-00019 Download citation * Received: 20 February 1989 * Accepted: 22 June 1989 * Issue

Date: 01 November 1989 * DOI: https://doi.org/10.1203/00006450-198911000-00019 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable

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