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

Abstract

S U M M A R Y1. 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 p-adrenoreceptors in different tissues reported for it in other species. It is suggested that P-receptors in the cat are less clearly differentiated and that they resemble those in man more closely than do those in other species.

Selectivity of Β‐adrenoceptor Agonists and Antagonists on Bronchial, Skeletal, Vascular and Cardiac Muscle in the Anaesthetized Cat

“…Other workers have found that the selectivity of P2adrenoceptor agonists is lower in the cat than in other laboratory species, for example the guinea-pig (Bowman & Rodger, 1972;Rodger, 1973;Houston & Rodger, 1974;Davey, Malta & Raper, 1974). Our results are consistent with this conclusion.…”

“…In this study the actions of a wide variety of /3adrenoceptor agonists and of two P-adrenoceptor antagonists have been determined in a single species simultaneously on bronchial muscle, soleus muscle, blood pressure and heart rate. The cardiovascular and soleus muscle actions of three of the agonistssalbutamol, orciprenaline and trimetoquinolhave been described previously (Bowman & Nott, 1970;Apperley & Daly, 1972;Houston & Rodger, 1974). Our results agree closely with those of the previous reports.…”

“…Thus, it would appear that the effect of practolol on heart rate arises from its partial agonist action, whereas its effect on soleus muscle does not. (Bowman & Nott, 1970;Apperley & Daly, 1972;Houston & Rodger, 1974). Our results agree closely with those of the previous reports.…”

The effect of a selective 5‐HT2 antagonist, ketanserin, on the pulmonary responses to Escherichia coli endotoxin

“…at the beginning and end of inspiration). Details are given in the paper by Houston & Rodger (1974).…”

Actions of Tetrahydropapaveroline on the Cardiovascular System and Skeletal Muscles of the Anaesthetized Cat and on Guinea‐pig Soleus Muscle in Vitro

“…In view of this association of effects of sympathomimetic amines on the cat soleus and on slow motor units in man, the cat soleus preparation has been used to predict the tremorogenic activity of 0-adrenoceptor agonists in man. It is used in particular in the pre-clinical assessment of sympathomimetic bronchodilators, and its value in this respect has been substantiated by a correlation between the potencies of drugs in depressing the cat soleus (Bowman & Nott, 1970;Gwee et al, 1972;Houston & Rodger, 1974) and in causing tremor in man (Watson & Richens, 1974;Marlin & Turner, 1975). Because of its typical 0-adrenoceptor-mediated depressant action on the soleus, THP is thus likely to exert direct tremorogenic actions on muscle fibres of slow motor units in man.…”