In-vitro characterization of the pharmacological effects induced by (–)-α-bisabolol in rat smooth muscle preparations

Abstract

The present study deals with the pharmacological effects of the sesquiterpene alcohol (–)-α-bisabolol on various smooth-muscle preparations from rats. Under resting tonus, (–)-α-bisabolol (30–300 µmol/L) relaxed duodenal strips, whereas it showed biphasic effects in other preparations, contracting endothelium-intact aortic rings and urinary bladder strips, and relaxing these tissues at higher concentrations (600–1000 µmol/L). In preparations precontracted either electromechanically (by 60 mmol/L K+) or pharmacomechanically (by phenylephrine or carbachol), (–)-α-bisabolol showed only relaxing properties. The pharmacological potency of (–)-α-bisabolol was variable, being higher in mesenteric vessels, whereas it exerted relaxing activity with a lesser potency on tracheal or colonic tissues. In tissues possessing spontaneous activity, (–)-α-bisabolol completely decreased spontaneous contractions in duodenum, whereas it increased their amplitude in urinary bladder tissue. Administered in vivo, (–)-α-bisabolol attenuated the increased responses of carbachol in tracheal rings of ovalbumin-sensitized rats challenged with ovalbumin, but was without effect in the decreased responsiveness of urinary bladder strips in mice treated with ifosfamide. In summary, (–)-α-bisabolol is biologically active in smooth muscle. In some tissues, (–)-α-bisabolol preferentially relaxed contractions induced electromechanically, especially in tracheal smooth muscle. The findings from tracheal rings reveal that (–)-α-bisabolol may be an inhibitor of voltage-dependent Ca2+ channels.