Abstract
A new monoterpene, paeoniflorigenone (PFG) (100-900 μg/ml), which was isolated from paeony 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 μg/ml) on twitching was not reversed by neostigmine (60 μg/ml) and was restored by washing out of PFG. PFG (150 μg/ml) depolarized the diaphragm muscle membranes by 10 mV and did not change the electrotonic potentials. PFG (100 μg/ml) inhibited weakly acetylcholine (5 μg/ml)-induced slow contractions. These results demonstrated that PFG is a depolarizing neuromuscular blocking agent, being similar to succinylcholine, except that PFG did not produce any contraction, but succinylcholine did.
