EFFECTS OF EXTRACTS OF PARS NEURALIS 



reduction (due to a vascular change or a ureteral spasm^ or 

 both?) followed by a considerable increase in the rate at 

 which the urine flows from the ureters; a phase of lessened 

 urinary secretion may then appear. It appears that this 

 effect is almost always accompanied by changes (usually an 

 increase) in the flow of blood through the kidneys. Probably 

 this diuretic efi^ect has little in common with the diuresis- 

 inhibiting efi-'ect so easily observed in unanesthetized mam- 

 mals. However, both changes are due to the vasopressor 

 principle. 



The view held by most investigators is that the transient 

 diuresis induced by the intravenous injection of a posterior- 

 lobe extract or the vasopressor principle into anesthetized 

 animals is due to local renal circulatory changes, chiefly in 

 the glomeruli. An increased rate of urine formation may be 

 associated with an increased blood flow (Cushny and Lambie, 

 1 921) or may occur in spite of a diminished blood flow 

 (Richards and Plant, 1922). In the latter case it is postulated 

 that an increased constriction of the glomerular efferent 

 vessels has occurred so that the blood pressure within the 

 glomeruli has been raised with a consequent increase in the 

 rate of filtration of the urine. It is also possible that the blood 

 is circulating through a greater number of glomeruli.'' 



During the diuresis caused by a posterior-lobe extract the 

 oxygen consumption of the kidney is not increased (Knowl- 

 ton and Silverman, 191 8). The urine of posterior-lobe diu- 

 resis contains an increased amount of chloride — both relative 

 (percentage) and absolute (Lomikowskaja, 1929; Nelson, 

 1934). Diuresis induced by the injection of solutions of 

 NaCl (hypertonic) or urea (5-10 per cent) is increased by the 

 additional intravenous administration of a posterior-lobe ex- 



3 Mackersie (1924) and McFarlane (1926). Under some conditions the immedi- 

 ate cessation of urinary secretion is not due to a spasm of the ureters (Ross and 

 Stehle, 1930). 



•* See also Frey (1926); McFarlane (1926); Macdonald (1933); and Nelson (1934). 



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