Effects of Neuromuscular Blocking Agents on Neuronal Nicotine Receptors of Motor Nerves: Blockade of Nicotinic Autofacilitation and Backfiring

ABSTRACT Tubocurarine reduced (60%) [3H]acetylcholine release from the isolated rat phrenic nerve at concentrations of 1 or 10 μM, but blocked backfiring of the phrenic nerve occuring after partial blockade of cholinesterase already at a concentration of 100 nM. The distinct potency of tubocurarine suggests differences between the presynaptic nicotine receptors mediating autofacilitation of release and preterminal nicotine receptors mediating backfiring of the motor nerve or a low agonist concentration at the latter receptors. The new neuromuscular blocking agents atracurium, pancuronium and vecuronium less effectively reduced [3H]acetylcholine release than tubocurarine indicating a lower a…