A patient on a ganglionic blocker for hypertensive emergency is unable to urinate. Which receptor subtype, when blocked at the parasympathetic ganglion, is primarily responsible for this effect?

• A Nicotinic N2 (ganglionic) receptor ✓
• B Muscarinic M3 receptor
• C Alpha-1 adrenergic receptor
• D Beta-2 adrenergic receptor

Explanation

Ganglionic blockers such as trimethaphan and hexamethonium act by blocking nicotinic N2 (Nn) receptors at both sympathetic and parasympathetic ganglia. Blockade of parasympathetic ganglia supplying the bladder detrusor reduces the cholinergic drive to the detrusor, causing urinary retention. Muscarinic M3 receptors are at the neuroeffector junction, downstream of the ganglion, and are not the site of action of ganglionic blockers.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.