AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 4 571-G575, Copyright © 1990 by American Physiological Society
Development of gastric antral smooth muscle contractility in newborn rabbits
J. Zitterman and J. P. Ryan
Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Muscle strips from newborn and adult rabbits were stimulated with
acetylcholine (ACh; receptor activation), potassium (membrane
depolarization), and calcium (skinned muscle preparation). The study was
designed to determine whether postnatal development is associated with
agonist-specific increases in force development or with an overall increase
in antral smooth muscle contractility. The results can be summarized as
follows. 1) Antral smooth muscle from newborn animals developed less active
force than tissues from adult animals when stimulated with ACh. 2) Antral
smooth muscle from newborn animals developed less active force than tissues
from adult animals when stimulated with potassium. 3) Skinned muscle
preparations from newborn animals developed less active force than skinned
muscle fibers from adult animals when stimulated with calcium. The data
suggest that the overall contractility of antral smooth muscle from the
newborn is less than that of the adult and that the difference can be
attributed, at least in part, to factors past the level of the membrane.
The study does not rule out the possibility that differences might also
exist with respect to the availability or mobilization of calcium.
