Effect of methacholine on acid and pepsin responses to pentagastrin in cats with innervated and denervated fundic pouches.

The effect of threshold dose of methacholine on gastric secretion stimulated by pentagastrin (PG) was studied in two groups of cats, four with Pavlov pouches (PP) and four with Heidenhain pouches (HP). In the PP group methacholine did not alter the maximal response (MR) and the dose producing half of the maximal response (D50) for PG. In the HP group the highest acid response to PG combined with methacholine was greater than the MR to PG alone. Methacholine decreased the D50 for PG in the HP group to that in the PP group with and without methacholine. Methacholine increased the pepsin response to all doses of PG both in the PP and the HP groups. The effect was more pronounced in the HP group. In both types of pouches, the percentage increase of pepsin secretion was larger at low than at high doses of PG. Methacholine increased the pepsin/acid (P/A) ratio for PG in the HP group to that in the PP group with and without methacholine. Accordingly, methacholine sensitized the oxyntic glands and increased the pepsin response to PG in the HP group as did basal vagal tone in the PP group. Methacholine did not further sensitize the innervated oxyntic glands to gastrin but increased the response of the peptic glands.