Quantitative analysis on isolated organs of the autonomic blocking properties of indoramin hydrochloride (Wy 21901)

Abstract

Summary Indoramin is a competitive α‐adrenoceptor blocking agent on the guinea‐pig isolated vas deferens and aortic strip; the pA2 value on the aorta is 7·4. Indoramin is devoid of β‐adrenoceptor blocking activity on the guinea‐pig isolated trachea (10–4m) and the Langendorff preparation of the rabbit heart (10−6m). It also has no adrenergic neurone blocking action on the Finkleman preparation of the rabbit small intestine (10−5m). On the Langendorff preparation of the rabbit isolated heart, indoramin (above 10−6m) has cardio‐inhibitory properties similar to those of propranolol. On the guinea‐pig isolated ileum (10−5m) and trachea (10−6m), indoramin is devoid of anticholinergic activity, but has a potent antihistamine action which satisfies the criteria for competitive antagonism; the pA2 value for this antagonism on the ileum is 8·2. Indoramin antagonizes 5‐hydroxytryptamine on the rat isolated fundus and ileum; the pA2 value for the antagonism on the ileum is 60.