Tolterodine used in overactive bladder acts by which receptor:

**Core Concept**
Tolterodine is an antimuscarinic agent used to treat overactive bladder symptoms, such as urgency, frequency, and incontinence. It works by inhibiting the action of acetylcholine at muscarinic receptors in the bladder.

**Why the Correct Answer is Right**
Tolterodine selectively blocks muscarinic receptors, specifically M3 receptors, in the bladder smooth muscle. This blockade reduces bladder contractions and increases bladder capacity, providing relief from overactive bladder symptoms. The M3 receptors are responsible for mediating the parasympathetic stimulation of the bladder, and blocking these receptors leads to a decrease in bladder contractility.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because tolterodine does not primarily act on nicotinic receptors, which are involved in neuromuscular transmission and not directly related to bladder function.

**Option B:** This option is incorrect because tolterodine is not a direct agonist of dopamine receptors, which are involved in various physiological processes, including motor control and reward.

**Option C:** This option is incorrect because tolterodine is not a direct antagonist of adrenergic receptors, which are involved in the sympathetic nervous system and not directly related to bladder function.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that antimuscarinic agents like tolterodine can have anticholinergic side effects, such as dry mouth, constipation, and blurred vision, due to their action on muscarinic receptors in various parts of the body.

**Correct Answer:** C.