The Effect of Atropine on Acid Secretion Stimulated by Acetylcholine, Histamine and Gastrin in the Isolated Whole Stomach of the Rat

Abstract

An isolated stomach preparation from immature rats has been used to study the effect of atropine on gastric acid secretion. The acid secretory response to acetylcholine was not inhibited by atropine at a concentration of 0.3 μM. Concentrations of atropine of 1 to 3 μM produced a measurable inhibition of acid secretion, and a concentration of atropine of 10 μM caused a complete block of acid secretion which could not be surmounted by high concentrations of acetylcholine. The acid secretory response to histamine was not inhibited by concentrations of atropine of up to 1 mM. Concentrations of atropine of 1 μM and 10 μM did not inhibit gastrin‐stimulated acid secretion, although a significant inhibition of acid output was observed with atropine at concentrations of 0.1 mM and 1 mM. These findings are discussed in relation to the role of cholinergic mechanisms in the control of gastric acid secretion.

Cholinergic Pathway of Gastric Acid Secretion in the Isolated Whole Stomach of the Mouse

“…high concentrations of atropine did not lower basal acid output indicating that the background cholinergic tone in the isolated stomach of the mouse, if at all in existence, is very low. Similar results were found by Bunce et al ( 1977). The H2-receptor antagonists, cimetidine and metiamide in agreement with previous observa tions ( Wan, 1977).…”

“…However, it contrasts with the study of Kowalewski and Kolodej (1974) who found that metiamide exhibits some block ing activity at the cholinergic receptor in the isolated canine stomach. High concentrations of atropine did not diminish histamine-induced acid secretion in the isolated stomach, as shown in the present and some previous studies (Bunce et al, 1977;Goto and Watanahe, 1975). All these results under in vitro circumstances are in contrast to those of in vivo studies with dif ferent mammalian species (Lick et al, 1967;Britnblecombe et al 1975;Grossmann and Konturek, 1974).…”

“…The slopes of 0.91 and 1.10, respectively, are not signif icantly different from unity and correlate with other results (Thorpe and Durbin, 1972;Angus and Black, 1979). By contrast, Bunce et al (1977) could not confirm these results. Their investigations using isolated whole stomachs of immature rats provided no evidence to support that atropine inhibits cholinergically induced acid secretion in a competitive manner.…”

“…To eliminate possible complicating factors involved in in vivo experiments, several groups have developed isolated stomach preparations of different design to study the characteristic of cholinergic stimulation Durbin, 1969\Shoemaker et al, 1970;Kowalewskiand Kolodej, 1974;Brennan et al, 1975;Bunce et al, 1977;Wan, 1977). The use of isolated organs minimizing vascular, hormonal and neu ral influences provide much information about stimulatory pathways.…”

The effect of α2‐adrenoceptor agonists on the acid secretory responses of rat isolated gastric mucosa to electrical field stimulation

“…The concentration ofidazoxan required to antagonize the inhibitory effect of UK-14,304 on acid secretion resulting from field stimulation was substantially greater than those which are effective in other in vitro systems such as guinea-pig ileum and rat vas deferens preparations where concentrations in the range of 40 and 400 nM idazoxan have been used to displace the concentration-response curve for clonidine (Doxey et al, 1983 (Angus & Black, 1979;Bunce et al, 1977). Angus & Black (1979) found that the pKB for atropine when measured against bethanechol-induced acid secretion was significantly lower than in the perfused isolated stomach of the mouse when measured against bethanechol-induced smooth muscle contraction.…”