Reversal of sympathomimetic bronchodilation by dichloroisoproterenol.

Abstract

In anesthetized dogs, the bronchodilation induced by epinephrine, norepinephrine, or sympathetic nerve stimulation can be reversed into a bronchoconstrictor response by DCI. The bronchoconstrictor response can be blocked by tolazoline. The bronchodilation induced by isoproterenol can be blocked completely by DCI. These results are interpreted to indicate that the bronchial smooth muscles contain alpha receptors which cause bronchoconstriction, and beta receptors which cause bronchodilation. The pulmonary vascular smooth muscles behave in a manner similar to the bronchiolar smooth muscles except that in the absence of either blocking agent, epinephrine induces vasoconstriction.