Pirenzepine acts on which receptor ?
**Core Concept**
Pirenzepine is a selective M1 muscarinic receptor antagonist used in the treatment of peptic ulcers. It acts by inhibiting the parasympathetic stimulation of gastric acid secretion.
**Why the Correct Answer is Right**
Pirenzepine selectively binds to the M1 muscarinic receptor subtype, which is predominantly found in the gastric glands and plays a crucial role in regulating gastric acid secretion. By blocking the M1 receptor, pirenzepine reduces the parasympathetic stimulation of gastric acid secretion, thereby decreasing acid production in the stomach. This mechanism of action is distinct from other muscarinic receptor antagonists, such as atropine, which have a broader spectrum of action.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pirenzepine does not act on the M2 muscarinic receptor subtype, which is primarily involved in regulating heart rate and cardiac function.
**Option B:** This option is incorrect because pirenzepine does not act on the D2 dopamine receptor, which is involved in regulating various physiological processes, including movement and mood.
**Option C:** This option is incorrect because pirenzepine does not act on the alpha-1 adrenergic receptor, which is involved in regulating smooth muscle contraction and blood pressure.
**Clinical Pearl / High-Yield Fact**
Pirenzepine is a selective M1 muscarinic receptor antagonist, which makes it a useful treatment option for peptic ulcers without causing the typical anticholinergic side effects associated with non-selective muscarinic receptor antagonists.
**Correct Answer: C. M1 muscarinic receptor**