Sigma receptor modulation of the muscle relaxant action of eperisone

We examined the mechanism of the muscle relaxant action of eperisone, using Straub tail and binding studies. In vivo, eperisone (50 and 100 mg/kg i.p.) produced a dose-dependent inhibition of the Straub tail in mice and this inhibitory effect was significantly reversed by haloperidol (0.5 mg/kg i.p.). This drug in itself had no effect on the Straub tail. Sulpiride (50 mg/kg i.p.) failed to reverse the inhibitory effect of eperisone. In vitro, (+)-3-(3-[3H]hydroxyphenyl)-N-(1-propylpiperidine) ((+)-[3H]3-PPP) specific binding, in rat brain membrane, was prevented by eperisone and the IC50 value was 0.43 nM. The muscle relaxant action of eperisone may be modulated by sigma receptors.