AJP - Gastrointestinal and Liver Physiology, Vol 239, Issue 4 295-G299, Copyright © 1980 by American Physiological Society
Actions of pentagastrin on smooth muscle of isolated dog intestine
J. J. Stewart and T. F. Burks
Adult dogs were anesthetized and segments of small intestine were isolated
and perfused via a mesenteric artery with Krebs-bicarbonate solution.
Muscle responses were monitored with extraluminal force transducers
implanted along the circular and longitudinal axes of the segments or by
means of an intraluminal balloon. Agonists were administered as
intra-arterial bolus injections in volumes not exceeding 0.1 ml.
Antagonists were dissolved in the Krebs perfusion solution. Smooth muscle
responses to pentagastrin (25 microgram), dimethyl-phenylpiperazinium
(DMPP, 5 microgram), and bethanechol (BeCh, 5 microgram) were reduced
during perfusion with atropine sulfate (25 ng/ml). Responses to DMPP (5
microgram) and pentagastrin (25 microgram) were diminished by perfusion
with tetrodotoxin (20 ng/ml) and after depolarizing doses of nicotine (500
microgram), whereas responses to BeCh (5 microgram) were unaffected in both
cases. Hexamethonium (10 microgram/ml) reduced responses to DMPP (5
microgram) but did not affect responses to BeCh (5 microgram) or
pentagastrin (5 microgram). Responses to DMPP (5 microgram) were not
reduced in segments desensitized to pentagastrin. The results suggest that
the stimulatory effect of pentagastrin on isolated dog intestine results
from an interaction of the peptide with nonnicotinic cholinergic receptors
on postganglionic cholinergic nerves.
