AJP - Gastrointestinal and Liver Physiology, Vol 249, Issue 6 668-G673, Copyright © 1985 by American Physiological Society
Interaction between stimuli and their antagonists on frog esophageal peptic glands
T. Shirakawa and B. I. Hirschowitz
The peptic glands, which are located in the mucosa of the distal esophagus
in the frog, respond to multiple stimuli. In vitro studies were performed,
using mucosal sheets of the esophagus of Rana catesbeiana, during the
summer months when the glands are fully responsive to determine whether the
receptors for the stimuli [cholinergic, beta-adrenergic, and peptidergic
(bombesin but not cholecystokinin)] are specific to the stimuli. Through
the use of three classes of antagonist, we found that 1) atropine defined
the muscarinic nature of the bethanechol stimulation, 2) propranolol
defined the beta-adrenergic nature of stimulation by isoproterenol, and 3)
the substance P analogue [D-Arg1,D-Pro2,D-Trp7,9,Leu11]substance P was
specific for the peptide bombesin. No cross-inhibition was seen, and
dibutyryl cGMP did not inhibit any of the three stimuli. Moreover, any two
of the three stimuli in combination stimulated more pepsinogen than either
alone but the same as the sum of the two individual responses. Both lines
of evidence indicate that there are at least three independent receptor
pathways for stimulation of pepsinogen secretion in these glands.
