ACTIONS OF THE SYMPATHOMIMETIC BRONCHODILATOR, TRIMETOQUINOL (AQL 208) ON THE CARDIAC, RESPIRATORY AND SKELETAL MUSCLE SYSTEMS IN THE ANAESTHETIZED CAT, AND ON CAT ISOLATED ATRIAL AND TRACHEAL PREPARATIONS

SUMMARY 1. The actions of the sympathomimetic bronchodilator trimetoquinol (AQL 208) have been compared with those of laevoisoprenaline on the cardiac, respiratory and skeletal muscle systems of the cat under chloralose anaesthesia, and on cat isolated atrial and tracheal preparations. 2. Trimetoquinol injected intravenously ranged in potency from two to four times less potent to about four times more potent than laevoisoprenaline in different in vivo experiments. Despite such wide variations in absolute potency the mean effective doses of trimetoquinol in both in vitro and in vivo studies were not significantly different (P>0.05) from those of laevoisoprenaline. 3. The effect on the soleus muscle is considered to be analogous to the muscle tremor that often occurs in man, and the results suggest that systemic administration of trimetoquinol may produce muscle tremor as an unwanted side effect in some patients. 4. Trimetoquinol, in the cat, shows no evidence of the selectivity for β‐adreno‐receptors in different tissues reported for it in other species. It is suggested that β‐receptors in the cat are less clearly differentiated and that they resemble those in man more closely than do those in other species.