Bungarotoxin [bung-garoh-TOK-sins] is a fast-acting lethal toxin that is the primary component of venom from the South Asian snake called a krait. It blocks nerve transmission at cholinergic [koh-luh-NUR-jik] synapses by competing with acetylcholine [uh-seet-I-KOH-leen] to bind irreversibly at the acetylcholine receptor. Which of the following would be LEAST LIKELY to also impact nerve transmission at the cholinergic synapses?