Effect of Magnesium on Vascular Spasm in Rats

In a previous study it was demonstrated that the magnesium ion is capable of preventing the contraction of smooth muscle both in vitro and in vivo.¹In a large percentage of guinea-pigs passively sensitized to horse serum an intravenous injection of magnesium chloride just prior to the injection of a shocking dose of horse serum prevented the appearance of anaphylactic shock. Similarly, the addition of magnesium chloride in isotonic amounts to the fluid of the Dale bath in which were suspended uterine strips from sensitized guinea-pigs prevented the contraction of the strips when antigen was added. EXPERIMENTS The present studies were concerned with the effect of the magnesium ion on the contraction of the smooth muscle of the vascular system in the intact animal. White rats (Wistar strain) were utilized as the experimental animals, and the systolic blood pressure was used as an index of the presence or absence