RESUMO
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 Ca(2+) channels.
Assuntos
Contração Muscular/efeitos dos fármacos , Relaxamento Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Sesquiterpenos/farmacologia , Animais , Carbacol/antagonistas & inibidores , Carbacol/farmacologia , Cistite/induzido quimicamente , Cistite/tratamento farmacológico , Modelos Animais de Doenças , Duodeno/efeitos dos fármacos , Duodeno/fisiologia , Ifosfamida , Técnicas In Vitro , Inflamação/induzido quimicamente , Inflamação/tratamento farmacológico , Masculino , Sesquiterpenos Monocíclicos , Contração Muscular/fisiologia , Relaxamento Muscular/fisiologia , Músculo Liso/fisiologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/fisiologia , Ovalbumina , Fenilefrina/farmacologia , Ratos , Ratos Wistar , Traqueia/efeitos dos fármacos , Traqueia/fisiologia , Bexiga Urinária/efeitos dos fármacos , Bexiga Urinária/fisiologiaRESUMO
The effects of the essential oil of Eucalyptus tereticornis (EOET), especially the effects of its constituents alpha- and beta-pinene, were studied on rat trachea in vitro. In tracheal rings, EOET, alpha- or beta-pinene potentiated the contractions induced by acetylcholine (ACh). Contractions induced by K(+) (60mM) were also potentiated by alpha- and beta-pinene, but were reduced by EOET. Our findings show that EOET has myorelaxant effects on rat airways, but potentiates ACh-induced contractions. Monoterpenes alpha- and beta-pinene are involved in its potentiating actions, but are not responsible for its myorelaxant effects. A putative inhibition of the acetylcholinesterase enzyme is involved.