Abstract
The analeptic drug pentamethylenetetrazol (Metrazol) used in the treatment of cardiovascular conditions has been reported 1 to produce dilatation of the abdominal capillaries. Because of the extensive clinical use of this drug, 2 it was felt desirable to restudy its action on the intact splanchnic vascular bed of the dog.
For this study we used 23 female dogs, the average weight being 7 kg. The anesthetic employed was chloralosane—80 mg. per kg. injected intravenously. Blood pressure and respiration were recorded in the usual manner. Oncometers were placed on the spleen and small intestine or a loop of ileum was exteriorized and kept in a chamber containing normal saline at body temperature. The mesentery of this loop was transilluminated from below and the vessels were observed through a lens system whose magnifying power could be varied at will.
Following a control period with observation on the blood vessels of an intestinal loop, the drug was injected intravenously as a 10% solution. The dosage ranged from 0.25 cc. to 2.0 cc. per injection and each animal received several injections during a period of 2 to 3 hours. In some instances the same dose was employed throughout a single experiment; in others, the dosage was varied. Almost continuous observations were made of the caliber of the large and small arteries, the arterioles and venules and the large and small veins. Any changes noted were correlated with the normal variation as established before the administration of the drug.
In a series of 12 animals, the predominant effect of the drug on the entire splanchnic circulation was constriction in 3 cases and dilatation in 3 others. There was no significant effect in the remaining 6 dogs.
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