Uterine relaxant effect of zolpidem: a comparison with other smooth muscle relaxants

Zolpidem is an imidazopyridine sedative-hypnotic which interacts with central benzodiazepine-receptors. To examine its effects on uterine smooth muscle we have compared with those obtained by diltiazem, papaverine and diazepam on different experimental models. The IC50 values obtained indicate similar behaviour of zolpidem and diazepam. They showed more active against the spontaneous contractions and those induced by KCl (60 mM) or by CaCl2 (0.01-10 mM) in Ca(2+)-free depolarizing medium than against acetylcholine (0.1 mM)-induced contractions. Both of them also showed more effectiveness against the tonic component of the acetylcholine-evoked contraction than against the phasic one. All the drugs tested were less powerful against contractions induced by oxytocin than against those induced by other agonists. This observation let us speculate that the mechanism of action of zolpidem may be related to an action on Ca2+ influx through voltage-dependent Ca2+ channels due to an interaction with low affinity receptor located at the plasmalemma as has been suggested for diazepam.