Effect of total alkaloids of Fissistigma oldhamii on cAMP and isolated hearts

The total alkaloids isolated from Fissistgma oldhamii (Hemsl.) Merr. (AFO) contained 4 alkaloids: xylopine and 3 new alkaloids(fissistigma A,B,C). In the isolated guines pig hearts AFO showed negative inotropic and chronotropic effects, increased coronary blood flow and antagonized the coronary vasoconstrictive action of pituitrin. In the isolated rat right artia AFO antagonized positive chronotropic effects of Ca++ 1,2.5,4 mmol/L and reduced spontaneous beats. The right shift of dose-response curve of isoproterenol, caused by AFO, was not parallel and exhibited a non-competitive antagonism. AFO relaxed the smooth muscles of trachea and small intestine in guinea pigs and rabbits. Propranolol reduced coronary blood flow and constricted the trachea. In mice and guinea pigs AFO elevated,but propranolol lowered, the levels of cAMP in plasma, liver and spleen. In mouse heart the changes of cAMP levels was not significant. These results proved that AFO was not a beta-receptor blockader.