**Question:** The following agent decreases gastric motility except?

A. Atropine
B. Proglumide
C. Dicyclomine
D. Cisapride

**Core Concept:** Gastric motility is the involuntary contractions of the stomach wall that facilitate digestion and emptying of food into the small intestine. Agents that affect gastric motility can either increase or decrease it.

**Why the Correct Answer is Right:** Cisapride is a selective 5-hydroxytryptamine type 4 receptor (5-HT4) agonist. By activating the 5-HT4 receptors, it increases gastric motility (specifically, it increases the frequency and amplitude of migrating motor complexes in the stomach).

**Why Each Wrong Option is Incorrect:**

A. Atropine is a muscarinic antagonist, meaning it blocks the action of acetylcholine at muscarinic receptors, including the parasympathetic receptors in the gastrointestinal tract. By blocking these receptors, atropine decreases gastric motility.

B. Proglumide is an antagonist at the cholecystokinin (CCK) receptor, which is involved in the regulation of gastric emptying and motility. Proglumide decreases gastric emptying but does not directly affect gastric motility, making it correct in this context.

C. Dicyclomine is a B-receptor antagonist, which means it blocks the action of acetylcholine on B-receptors in the gastrointestinal tract. By blocking these receptors, dicyclomine decreases gastric motility.

Dicyclomine is a B-receptor antagonist, which means it blocks the action of acetylcholine on B-receptors in the gastrointestinal tract. By blocking these receptors, dicyclomine decreases gastric motility.

**Clinical Pearl:** Dicyclomine is often used in clinical practice to treat gastrointestinal disorders like irritable bowel syndrome (IBS) due to its anticholinergic properties.

**Correct Answer Explanation:** Cisapride directly affects gastric motility and is therefore the correct answer, while Atropine, Proglumide, and Dicyclomine indirectly affect gastric motility through their actions on muscarinic, CCK, and B-receptors respectively.