Blocking Effects of a New Component, Paeoniflorigenone, in Paeony Root on Neuromuscular Junctions of Frogs and Mice

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Abstract
A new monoterpene, paeoniflorigenone (PFG) (100-900 .mu.g/ml), which was isolated from peony roots and identified chemically, suppressed both indirectly and directly stimulated muscle twitchings of frog sciatic nerve-sartorius muscle preparation, and it indirectly stimulated muscle twitchings of phrenic nerve-diaphragm muscle preparations. The suppression effect by PFG (300 .mu.g/ml) on twitching was not reversed by neostigmine (60 .mu.g/ml) and was restored by washing out of PFG. PFG (150 .mu.g/ml) depolarized the diaphragm muscle membranes by 10 mV and did not change the electrotonic potentials. PFG (100 .mu.g/ml) inhibited weakly acetylcholine (5 .mu.g/ml)-induced slow contractons. PFG evidently is a depolarizing neuromuscular blocking agent, being similar to succinylcholine, except that PFG did not produce any contraction, but succinylcholine did.