The effect of intravenous noradrenaline on the oxygen consumption of new‐born mammals

It is well known that adrenaline, administered by intravenous injection to adult animals, causes a rise in 02 consumption, in heat production and in rectal temperature. Noradrenaline and other sympathomimetic amines have a similar but less powerful action. In most adult animals noradrenaline has about one tenth of the activity of adrenaline in this respect (Ellis, 1956). However, there is evidence which suggests that the situation may be different in new-born animals. Moore & Underwood (1960a), working with young kittens, showed that subcutaneous injection of 100-10O0g noradrenaline/kg caused a rise in 02 consumption of 30-100 % lasting an hour or more. Adrenaline was less effective. In one experiment intravenous infusion of 6 7,g noradrenaline/ kg/min also caused a rise in 02 consumption. Karlberg, Moore & Oliver (1962) have shown that intravenous infusion of noradrenaline in new-born babies causes a rise in 02 consumption. It was suggested that noradrenaline might be a 'regulator of heat production' in the new-born animal (Moore & Underwood, 1960a). There is indeed much evidence to show that new-born animals are more dependent on chemical means of heat regulation than are adults. Thus, exposure of the new-born animal to a cool environment causes a large rise in 02 consumption, usually without overt shivering or increase in skeletal muscular activity. This has been shown not only in species which are relatively mature at birth, but is particularly obvious in those born in an immature condition, such as the rat (Taylor, 1960), rabbit (Giaja, 1925; Adamsons, 1959), cat (Leichtentritt, 1919; Hill, 1959) and dog (Gelineo, 1954; McIntyre & Ederstrom, 1958), and also in the rhesus monkey (Dawes, Jacobson, Mott & Shelley, 1960), and in human infants (Briuck, 1961). But before the hypothesis that this rise in 02 consumption is due to noradrenaline liberation can be seriously entertained, it has to be shown that intravenous administration of noradrenaline causes a significant elevation in 02 consumption, in the comparatively small quantities which