Carbachol's receptor activation profile is best described as:

• A. Activates both muscarinic and nicotinic receptors
• B. Activates only muscarinic receptors
• C. Activates only nicotinic receptors
• D. Inactivates acetylcholine receptors

Answer: (A)

Carbachol is a non-selective cholinergic agonist, meaning it can activate more than one type of acetylcholine receptor. It binds to and stimulates both muscarinic receptors, which mediate smooth muscle contraction and glandular secretion, and nicotinic receptors, which are found at autonomic ganglia and the neuromuscular junction. This dual receptor activation is why its profile is described as activating both muscarinic and nicotinic receptors. The other possibilities aren’t correct because they imply selectivity for only one receptor type or imply receptor inactivation, whereas carbachol acts as an agonist at both receptor families and does not inactivate receptors.