A note on the failure of pituitrin to sensitize the sympathetic system

In 1912 Kepinow published the conclusion that the injection of small quantities of pituitary extract “sensitizes” the point of attack of epinephrin. 1 His observations were that a given dose of epinephrin produced a greater mydriatic effect in rabbits and cats, a greater vasoconstriction in the Loewi-Trendelenberg frog preparation and a greater vasomotor effect in rabbits and dogs if immediately before hand a minimal dose of pituitary preparation had been injected. Kepinow's work has been quoted as the basis for a rather far reaching conclusion that the pituitary gland has normally the function of promoting the activity of the sympathetic nervous system.

In various researches on the vasomotor system we have had occasion to use pituitary extract in connection with epinephrin and nicotin and it became important to know to what extent sympathetic sensitization occurs. As our previous work has been done exclusively on dogs we have investigated the matter in this species only. Kepinow used two kinds of pituitary material, an extract prepared by himself, and the commercial preparation “Pituitrin” made by Parke Davis and Co. Kepinow states that both preparations gave similar effects. Our experiments were made with “Pituitrin” only.

Since the results are negative they may be reported very briefly. The procedure was to determine the effects of injections of given quantities of “adrenalin” and of nicotin, selected to give a moderate rise of blood pressure. About I C.C. of adrenalin, I : 100,000, and I C.C. of nicotin I : 4,000 are suitable for mediumsized dogs. Having determined the reactions to these drugs, pituitrin was injected by vein in quantity to give a slight rise of pressure, e. g., .05 C.C. At various intervals from one half to several minutes after this injection, the adrenalin and nicotin injections were repeated.