BLOCKADE OF RESPONSES TO EPINEPHRINE ANT) NOREPINEPH- RINE BY DIBENAMINE CONGENERS’

The ability of members of the Dibenamine series of adrenergic blocking agents (13-haloalkylamines) to inhibit or “reverse ” vasopressor responses to a variety of sympathomimetic agents has been repeatedly demonstrated. With different stimulating agents the responses obtained after blockade vary from easily elicited, complete reversals of the pressor response (epinephrine, Kephrine, etc.) to re-sponses which usually retain a pressor component and in which a significant depressor phase can be demonstrated only under special conditions (aliphatic amines, norepinephrine, etc.). Because the pressor response to epinephrine is readily reversed whereas that to norepinephrine is usually only partially inhibited (Barger and Dale, 1910; Greer et al., 1937; Melville, 1937; de Vleeschhouwer, 1948; West, 1949; Euler, 1951), the adrenergic blocking agents have been em-ployed in tests to distinguish between epinephrine and norepinephrine. Conse-quently, it is now frequently assumed that the excitatory action of epinephrine is more readily inhibited than is that of norepinephrine. However, differences in the blood pressure response after blockade do not necessarily indicate difference