Abstract
Antitussive and respiratory effects of three newly synthesized methanobenzazonine derivatives and their d- and l-isomers were investigated to understand the relationship between the cough and respiratory centers. Antitussive effects were evaluated with the PEC (puncture electrode-induced cough) method in conscious guinea pigs. The respiration study was carried out in anesthetized guinea pigs. Intraarterial injections of d-, dl-, and l-ST-2123; d-, dl-, and l-TS-2121; and d-ST-2121 into the right carotid artery at a dose range of 0.2-0.8 mg caused no effect on respiration. dl-ST-2121 at 0.4 to 0.8 mg and l-ST-2121 at 0.2 to 0.8 mg depressed respiration dose-dependently. Codeine (0.2-0.8 mg) depressed respiration slightly. Morphine (0.2-0.8 mg) depressed respiration more strongly. All the methanobenzazonine derivatives used, when given intraperitoneally, showed antitussive potencies that were 1/3-1/2 the potency of codeine. The antitussive potencies of the d-, dl-, and l-isomers of the three derivatives used were discussed on the bases of chemical structures and drug receptors. These results provide evidence of a discrepancy between the cough and respiratory centers in the brain stem.
