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

Pediatric Research
T TomomasaP E Hyman

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 approximately 5 microM), the maximal response was nearly 4-fold greater in weanling (1140 +/- 73 mN/cm2) versus neonate (305 +/- 54 mN/cm2), p less than 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 less than 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 less than 0.001). ED50 for seroto...Continue Reading

Citations

Jan 1, 1992·Digestive Diseases and Sciences·P I IttmannC L Berseth
Oct 20, 2001·Pediatric Research·S ZangenP E Hyman
Jun 26, 2014·Pediatric Research·Frank EifingerMechthild M Schroeter
May 18, 1999·The American Journal of Physiology·W H PercyJ T Brunz

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