Final answer:
Non-depolarizing agents prevent muscular contraction by blocking nicotinic receptors at the neuromuscular junction, preventing acetylcholine from triggering depolarization. The correct option is D).
Step-by-step explanation:
Non-depolarizing agents work by blocking nicotinic receptors at the neuromuscular junction (NMJ). These receptors are normally activated by the neurotransmitter acetylcholine (ACh), which is released from motor neurons.
Non-depolarizing agents act as competitive antagonists to ACh, binding to the nicotinic receptors without activating them. This prevents ACh from binding and stops the flow of positive ions into the muscle cell, thereby preventing depolarization of the muscle cell membrane and muscular contraction.
Drugs that affect both divisions of the autonomic system may bind to or block nicotinic receptors as they are found in autonomic ganglia.
In contrast, Botox works differently by decreasing the release of acetylcholine from motor neurons, leading to muscle paralysis.
It's important to note the distinction between the mechanisms of non-depolarizing agents and other substances such as Botox or agents that inactivate the enzyme acetylcholinesterase, which are not the subject of this question.