Inhibition of acetylcholine-stimulated secretion in the isolated whole stomach of the rat

Abstract

Abstract The rat isolated whole stomach preparation has been used to investigate acetylcholine-stimulated pepsin secretion. Acetylcholine stimulated pepsin output in a dose dependent manner over the range 3 times 10−4 to 3 times 10−3 M. Metiamide (10−3 M) had no significant effect on the pepsin response to acetylcholine suggesting that histamine H2-receptors are not involved in this response. Atropine (2 times 10−8, 2 times 10−7 and 2 times 10−6 M) produced a dose-related inhibition of the pepsin output to 7 times 10−4 M acetylcholine, indicating that this response is mediated by muscarinic receptors. Pirenzepine also produced a dose-related inhibition of acetylcholine (7 times 10−4 M) stimulated pepsin output at 2 times 10−6, 2 times 10−5 and 2 times 10−4 M. Increasing the concentration of acetylcholine to 3 times 10−3 M completely reversed the effect of atropine (2 times 10−6 M) but pirenzepine (2 times 10−4 M) still produced a significant inhibition of acetylcholine-stimulated pepsin secretion. In each series of experiments acid and pepsin secretion responded in a similar manner to the effects of inhibitors, providing no evidence for a separation of these responses.