New types of bronchodilator agents, bi-and tricyclic nitrogen bridgehead compounds with a pyrimidin-4 (3H)-one ring, were synthesized and evaluated for bronchodilator activity against serotonin-, histamine-, and acetylcholine-induced spasms in the guinea pig Konzett- Rossler test. The structure-activity relationships are discussed. The effects of some bi-and tricyclic derivatives on the human bronchus were also investigated. The homologous ...