Abstract
That young animals are much less susceptible to anoxia than are adults has been well established. 1-3 4 5 Selle and Witten 4 . have shown that the respiratory center of rats, rabbits, cats and dogs is itself much more tenacious and viable in the young than in the adult, and that until approximately 6 weeks of age the survival of the respiratory mechanism of the rat is inversely proportional to age. Following decapitation or ligation of the cerebral vessels, the isolated ischemic head of a full grown rat gasps 5 to 8 times over a period of 10 or 20 sec and thereafter remains motionless; in a week old animal the phenomenon continues for 30 min or more.
Unlike adults, rats under 6 weeks of age display 2 periods of respiratory movements: and initial series which consists of 6 to 12 gasps and lasts 20 to 30 sec, and a second series which begins 30 to 50 sec after cessation of the initial of first series and lasts for a variable time depending upon the age. The total number of gasps in both series, as well as the total duration of gasping, is greater the younger the animal. The second series, which is influenced most by age, lasts 30 to 40 min in new-born animals. As age increases, the number of gasps, as well as duration of gasping, diminishes uniformly. Similar observations have been made on ischemic heads of rabbits, cats and dogs.
The present study was designed to determine the effectiveness of certain drugs on the activity of this primitive respiratory mechanism. Using a technique previously described 4 for determination of survival of this mechanism, a large number of this mechanism, a large number chemical agents (67) varying widely in composition and action, were injected subcutaneously or intraperitoneally into 12-15-day-old rats (weight 18-26 g). Following an interval ranging from min to several hours
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