Anticholinergic activity of bornaprine and its metabolites in the isolated rat atrium

These studies evaluated the antimuscarinic activity of bornaprine hydrochloride, a synthetic anticholinergic drug utilized in the treatment of parkinsonism. Several of its metabolites were also evaluated. Biological activity was assessed by the ability of the compounds to inhibit the negative inotropic response to carbachol in the isolated left atrium of the rat. Bornaprine showed a pA2 value (concentration required to reduce the agonist response by 50%) of 7.27 +/- 0.21. The exo and endo epimers were approximately equipotent in this regard. One metabolite, the 5-hydroxyl, showed similar activity to the parent compound, whereas 2 other hydroxylated metabolites showed much less effect.