Beta-adrenoceptor stimulating properties of para-dimethylaminobenzaldehyde.

1. Studies on the various isolated tissues indicate that para-dimethylaminobenzaldehyde (DMAB) is a beta-adrenoceptor stimulant. DMAB is antagonized by the beta-adrenoceptor blocking agent, MJ 1999, but not by the alpha-adrenoceptor blocking agent, phentolamine.2. A study of dose-response relationships suggests a competitive interaction between MJ 1999 and DMAB.3. DMAB was about 122 times less potent than isoprenaline on the isolated guinea-pig tracheal preparation. The effects of DMAB on isolated rabbit atria were not only very weak, but were also very brief. On this tissue, DMAB was respectively 72,000 and 55,400 times less active than isoprenaline in producing positive chronotropic and inotropic effects. DMAB caused the relaxation of the guinea-pig taenia coli and the rabbit ileum. These actions were very weak in comparison with those of isoprenaline.4. These results suggest that a compound (DMAB) structurally different from isoprenaline may mimic isoprenaline responses by stimulating beta-adrenoceptors through different mechanisms.