AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 2 388-R395, Copyright © 1989 by American Physiological Society
Excitatory and inhibitory effects of gastrin peptides on gastric motility in sheep
L. M. McLeay and M. H. Wong
Department of Biological Sciences, University of Waikato, Hamilton, New Zealand.
In conscious sheep, tetragastrin, pentagastrin, and synthetic human gastrin
I, injected either subcutaneously or intravenously in doses of 156-5,200
pmol/kg body wt, inhibited the vagally dependent cyclical motility of the
reticulum and rumen, whereas in vitro pentagastrin (10(-12) to 10(-6) M)
had no demonstrable inhibitory or excitatory effects on intrinsically
active or quiescent muscle of the reticulum, rumen, and omasal leaves. In
vitro pentagastrin (10(-18) to 10(-4) M) stimulated quiescent and
intrinsically active longitudinal and circular muscles of the body of the
omasum and the body and antrum of the abomasum and potentiated contractile
responses of antral muscle to electrical stimulation of intramural
cholinergic nerves. Responses in the presence of hexamethonium, atropine,
and tetrodotoxin indicated that the excitatory effects on mixed
nerve-muscle preparations of omasal and abomasal tissue were mediated both
through stimulation of cholinergic neurones and by direct actions on the
muscle. In vitro the ovine stomach shows marked regional differences in
both its response and sensitivity to gastrin peptides, and their inhibitory
effects on reticuloruminal motility in vivo appear to be other than direct.
