Oxygen consumption in new‐born rats

Abstract

The rectal temperature of the newborn rat closely approximates to that of its environment. The ability of the rat to maintain a relatively constant body temperature in the cold is fairly well developed by the age of 3 weeks. Adolph (1957) concluded, largely from the work of Antoschkina (1939) and Fairfield (1948), that the newborn rat does not respond to cold with an increase in heat production (as indicated by an increase in 02 consumption) until the age of 3-4 days. If this were true, then the newborn rat would differ from the newborn of most mammalian species in this respect. (1958) which suggest that the newborn rat is to some extent capable of increasing 02 consumption in the cold shortly after birth. As the newborn rat is now so widely used in experimental work it was decided to determine in more detail the influence of age on minimal O2 consumption , on the neutral environmental temperature at which 02 consumption is minimal, and on the maximal increase in 02 consumption that is observed with cooling. Observations were also made on the effect of varying the 02 content of the inspired air on the 02 consumption of young rats at the neutral environmental temperature, and on the effect of breathing 50 % 02 on the metabolic response to cold. A preliminary account of this work has been given (Taylor, 1960). METHODS Wistar rats of either sex were placed in a glass chamber which formed part of a closed system of about 300 ml. volume, through which air was circulated at approximately 1-5 1./min by means of an aquarium aerator. Carbon dioxide was absorbed by soda-lime, and the oxygen consumed in the system was replaced automatically. As 02 was consumed

Oxygen Consumption in the New‐born Rat and the Effects of Maternally Administered Analgesics

“…Hill (1959) found that for kittens maintained at the neutral temperature, the oxygen concentration of inspired air could be reduced to 10% before oxygen consumption was affected. However, more relevant is the report of Taylor (1960) …”

“…This, together with the small scatter and absence of seasonal change, provides grounds for confidence in the described technique, within its limitations, which might be included among tests to be used for the investigation of drugs administered at the time of childbirth. Fairfield (1948) 35-0 2-3 days 2-1-3-6 Gelineo & Gelineo (1951) 35.9 3-5 hr 1.90 Taylor (1960) 38-0 4 hr 1-97 Present study 38-0 4hr 180 The oxygen consumption of new-born from mothers treated with morphine, methadone or etorphine was reduced in proportion to the maternal dose level of narcotic, over a limited range, but no explanation can be offered for the apparently significant change in slope of the morphine response line at high doses (Fig. 2).…”

Chemical temperature regulation in new-born mice

“…Er stiitzte seine Auffassung dabei im wesentlichen auf die Untersuchungen yon ANTOSCHKINA (1939( ) und FAIRFIELD (1948. In sp~iteren Untersuchungen wurde jedoch nachgewiesen, dat~ auch bei der neugeborenen Ratte in den ersten Lebenstagen eine Steigerung der Sauerstoffaufnahme dutch Abkiihlung eintritt (GELINEO ~i;GELINEO 1951, HA~tN & KOLDOVSKY 1958, TAYLOR 1960 (PIcHOTKA 1960, 1961, CHOINOWSKI 1962, HOHNSTADTER 1962 GELIN~O & GEI.mEO 1951, BAI~Id 1953, TAYLOR 1960.…”

Development of homeothermy in infant C3H mice

“…If Ta is very low, the pup may not be able to reach an area of higher temperature, resulting in further heat loss, with subsequent hypothermic immobility, additional heat loss, and, eventually, death. Although vascular response to lowered Ta has been suggested as early as 4 days of age (Poczopko, 1961), most researchers have found little evidence of this ability until 12-14 days of age in the rat (e.g., Conklin et al, 1971;Taylor, 1960). Furthermore, because most mice and rats are born without fur, they lack both passive (insulation provided by fur) and active (piloerection) means of reducing the rate of heat loss that are available to the adult.…”