I The pharmacological actions of racemic noradrenaline, adrenaline, isoprenaline and N-tbutylnoradrenaline have been compared with those of their corresponding derivatives containing an oxymethylene (OXY) link between the ring and ethanolamine side chain. 2 The compounds were tested in the anaesthetized cat for their ability to produce positive chronotropic effects, bronchodilator actions, changes in perfusion pressure in the perfused hind limb and decreases in soleus muscle contractions. 3 All the OXY-derivatives were potent ,-adrenoceptor agonists. The inclusion of the oxymethylene link promotes selectivity for fIl-as opposed to fl2-adrenoceptor activity.4 In comparison with the parent compounds, the OXY-derivatives of adrenaline and noradrenaline had very weak a-adrenoceptor stimulant effects.

1. Racemic mixtures of noradrenaline, adrenaline, isoprenaline, N-t-butylnor-adrenaline and their corresponding derivatives containing an oxymethylene (OM) link between the phenyl ring and ethanolamine side-chain have been tested for their effects on beta-adrenoceptors in isolated guinea-pig atrial and tracheal preparations. 2. In atrial and in spontaneously contracted tracheal preparations both the parent catecholamines and their corresponding OM-derivatives had a similar order of potency as beta-receptor agonists. 3. In carbachol-stimulated tracheal preparations the OM-derivatives were shown to have partial agonistic actions. 4. As in other phenylethanolamines and phenoxypropanolamines, both the agonistic and antagonistic potency of the OM-derivatives increased with increasing amine substitution.

1. Soterenol and its 3-hydroxy, 4-methanesulphonamido isomer (MJ6987-1) were compared with isoprenaline for beta-adrenoceptor mediated effects in guinea-pig atrial, tracheal, uterine and ileal preparations. In addition, MJ6987-1 was tested for its effects in the atria of cats, rabbits and rats. 2. Soterenol had a lower intrinsic activity and was approximately two to six times less active than isoprenaline in all preparations. 3. MJ6987-1 was a full agonist, being some 30--200 times less active than isoprenaline at beta 1-receptor sites and greater than 3000 times less active in preparations where beta 2-receptor activation was involved. 4. Change in the position of the ring substituents in soterenol leads to the production of beta 1-receptor selective agonist.