AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 3 309-G315, Copyright © 1986 by American Physiological Society
Effects of tachykinins on gastric acid and pepsin secretion and on gastric outflow in the Atlantic cod, Gadus morhua
B. Holstein and C. Cederberg
Gastric acid and pepsin responses to substance P, physalaemin, eledoisin,
and an eledoisin-related peptide, [Lys6]eledoisin-(6-11), were measured in
gastrically and intestinally perfused cods. The intestinal perfusion
maintains water balance and inhibits drinking. During basal conditions acid
secretion was stimulated (approximately equal to 25%) by low doses (less
than 0.13 nmol X kg-1 X h-1) of physalaemin and eledoisin. High doses
(greater than 16 nmol X kg-1 X h-1) were inhibitory. Median and very high
doses of substance P and eledoisin-related peptide, respectively, tended to
stimulate acid secretion. All tachykinins were extremely efficacious
pepsigogues. Physalaemin and eledoisin were the most potent (D50
approximately 10(-10) mol X kg-1 X h-1) but produced fading and submaximal
responses at high doses. The fading persisted despite endogenous
acidification produced by histamine stimulation. Relative to physalaemin,
the potencies of substance P and eledoisin-related peptide were 0.04 and
0.001. The results suggest that some tachykinin may be a physiological
stimulator of pepsin secretion and that the effect on acid secretion
results from activation of both stimulatory and inhibitory pathways. The
inhibitory component probably includes a cholinergic link. Gastric volume
outflow increased during infusion of physalaemin, eledoisin, and (slightly)
substance P. The response, which was not related to acid secretory rate
(and conceivably not to volume secretion), suggests that a tachykinin may
be involved also in the regulation of drinking.
