100 



Scientific Proceedings (49). 



72 (681) 



On the action of the infundibular portion of the hypophysis 

 upon vasodilators. 



By J. AUER and S. J. MELTZER. 



[From the Department of Physiology and Pharmacology of the 

 Rockefeller Institute.] 



By the investigations of Oliver and Schafer, Howell and others, 

 it has been established that by intravenous injections of an extract 

 of the infundibular portion of the hypophysis a rise of blood 

 pressure is produced, which, however is usually not as strong as 

 the one produced by an injection of adrenalin. It is now generally 

 assumed that, like adrenalin, the rise is produced by a stimulation 

 of the constricting mechanism. On the basis of the hypothesis, 

 that the hypophysis may raise the blood pressure not by a stimula- 

 tion of the constricting, but by a depression of the vasodilating 

 mechanism, we studied the effect of stimulation of the depressor 

 nerve in rabbits soon after an intravenous injection of an extract 

 of the hypophysis. We used for this purpose the pituitrin of 

 Parke, Davis & Co., which is made up from the infundibular portion 

 of the hypophysis. In some of the experiments the pituitrin 

 was heated for the purpose of driving off the chloretone. In some 

 of the experiments both vagi were cut to eliminate the inhibitory 

 action through these nerves. 



We may state briefly that in every experiment the irritability 

 of the depressor nerve was either abolished or considerably reduced 

 for a few minutes after the injection of the pituitrin. This was 

 definite even before the rise which follows the injection began to 

 develop and also during an insignificant rise. The larger the 

 injected dose of pituitrin, the longer did the reduction of the irrita- 

 bility of the depressor nerve last. In 12 or 16 minutes, however, 

 the irritability, as a rule, returned to normal. On repeating the 

 injections, the reducing effect upon the irritability of the depressor 

 became less and less pronounced. 



We may recall here the fact, observed by Oliver and Schafer 

 and others, that during the rise of blood pressure from adrenalin, 

 stimulation of the depressor nerve is ineffective. But this applies 



