Blocking effects of blended paeoniflorin or its related compounds with glycyrrhizin on neuromuscular junctions in frog and mouse.

The combined effects of paeoniflorin (PF), a main component of paeony roots, and glycyrrhizin (GLR), a main component of licorice roots, were investigated on isolated sciatic nerve-sartorius muscle preparations in frogs, or on isolated or in situ phrenic nerve-diaphragm muscle preparations in mice, intending to explain the effects of "Shakuyaku-Kanzô-Tô, composed of both these Chinese drugs, on clinical neuropathy. PF and GLR used together blocked indirectly stimulated twitchings at concentrations which when used alone induced no blocking effects. PF and GLR at a combining ratio of 1:2 (weight concentrations) corresponding to the amounts contained in "Shakuyaku-Kanzô-Tô, was more potent than when they were used at the ratio of 1:1 or 2:1. The synergistic effects induced by GLR were also confirmed for the other components, paeoniflorigenone or oxypaeoniflorin, which are contained in paeony roots, and for succinylcholine. The blocking effect of d-tubocurarine were not increased by GLR. Concludedly, PF and GLR were found to cause the pharmacological blend effect. The two combined compounds were mainly therapeutic components in "Shakuyaku-Kanzô-Tô".