The characterization of the activity of a bark extract from Fagara martinicensis on the rat vas deferens

ABSTRACT

OBJECTIVE: An aqueous extract made from the bark of Fagara martinicensis (family Rutaceae) was examined for its effect on the isolated rat vas deferens. METHOD: The investigation involved measurement of isometric tension in the prostatic and epididymal portions of the isolated rat vas deferens which was anchored in an organ bath with physiological solution. Non-cumulative doses of Fagara martinicensis (FM) were added to the bath and the effects examined in the presence of receptor antagonists to characterize the actions of FM. Results before and after antagonist additions were compared. RESULTS: Non-cumulative addition of FM (1.6 mg/ml to 14.1 mg/ml) produced contractions of both portions of the vas deferens, with the epididymal portion showing greater sensitivity to the effects of FM. The contractions consisted of a rhythmic component superimposed on a phasic and tonic component. All components of the contractions were abolished by prazosin (2.1 uM), a selective a1-adrenoreceptor antagonist, and therefore it was concluded that FM contractions are due to agonist activities on these receptors. Since stimulation of a1-adrenoreceptora results in the mobilization of extracellular calcium into the muscle, the involvement of extracellular calcium was investigated with calcium channel antagonist, nifedipine (0.11-6.0 uM). Nifedipine inhibited all components of the contraction. This effect indicates that entry of extracellular calcium into the muscle was involved in all components of the contraction and further confirms a1-adrenoreceptor agonist action of Fagara martinicensis. CONCLUSIONS: Fagara martinicensis may therefore be a potential source of drugs with a1-adrenoreceptor agonist properties. (AU)