Effect of phenoxybenzamine on neural and humoral control of sweat glands.

It is evident that the role of phenoxybenzamine as an alpha adrenergic blocking agent is suspect in the sense that it, in concert with some other alpha adrenergic blocking agents, may display a low degree of specificity.1' 2 Other alpha adrenergic blocking agents the specificity of which has been questioned include bretylium and guanethidine. They have been described as exerting, in doses of from 10 to 30 times that for adrenergic nerve blockade, a curarelike (which is to say, an antinicotinic) action in cholinergic systems.3' 4 These latter two agents, considered by some as seemingly less controversial than phenoxybenzamine, will be discussed in a subsequent paper.5 In the meanwhile, and for present purposes, it is well to bear in mind that controversy exists concerning phenoxybenzamine. The reasons for using alpha adrenergic blocking agents in connection with study of transmission to, and chemical action on, sweat glands are simple. Cholinergic innervation of the sweat glands is established beyond peradventure.6 And yet the glands respond by secretion to injected noradrenaline, the action not being blocked by atropine, the anticholinergic (muscarinic) blocking agent that is so effective in blocking action by sudomotor impulses, injected acetylcholine, and injected pilocarpine.7. 8 An account of events leading to the foregoing statement is given in reference 9. Granting, as one must, that noradrenaline acts, the problem is to attempt evaluation of its role, if any, in neuroglandu