Selective blockade of β‐adrenoceptors by 1‐(p‐allylphenoxy)‐3‐isopropylamino‐2 propanol hydrochloride (H 64/52) in the anaesthetized dog

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Abstract
1 The β-adrenoceptor blocking properties of l-(p-allylphenoxy)-3-isopropylamino-2-propanol hydrochloride (H 64/52) on the cardiovascular and broncho-motor responses to isoprenaline have been determined in the anaesthetized dog. 2 H 64/52 selectively blocked the isoprenaline-induced increase in heart rate, contractile force and reduction in airway pressure in the same dose range. 3 H 64/52 produced a minimal blockade of vascular β-adrenoceptors which was apparent only when the isoprenaline-induced fall in diastolic pressure was considered. No significant vascular β-adrenoceptor blockade with H 64/52 could be shown with the femoral arterial flow or hind-limb perfusion studies. 4 These results further support the hypothesis that several different β-adrenoceptor subtypes exist in the dog. The β-adrenoceptors subserving cardiac stimulation and bronchodilation appear to be similar and both differ from the β-adrenoceptor subserving vasodilatation.