Maturation of tempeature homeostasis in the rat

Abstract

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Facial thermal input in the caudal trigeminal nucleus of rats reared at 30 degrees C.

“…A temperature of 33 0C was not used for heat adaptation in the present work as it is known that a temperature of 34 0C results in the eventual death ofall pre-weanling offspring, apart from depressive and deleterious effects ofsuch high temperatures on a wide range of physiological functions in the adult (Purves, 1964;Pennycuick, 1964a-d). The ability of rats to maintain their body temperature develops with age (Taylor, 1960;Thompson & Moore, 1968;Conklin & Heggeness, 1971;Fowler & Kellog, 1975) and it is conceivable that heat-rearing could modify the development of the thermoregulatory control system at one or more of a number of points in the system, for example thermal effectors, central comparison or thermal sensing. The last possibility is supported by the well documented effects of disuse on the mechanoreceptive projection in the trigeminal system (Killackey, 1973;Killackey & Belford, 1979Killackey, Belford, Ryugo & Ryugo, 1976;Waite & Taylor, 1978).…”

La thermogenèse induite par l'alimentation chez le rat Zucker âgé de 2 et 7 jours

“…Certains auteurs (Trayhurn et al, 1976 ;Schmidt et al, 1984 ;Stern et al, 1984) (Godbole et al, 19811, ), cependant elle confirme l'effet de la réalimentation sur le métabolisme énergéti-que des ratons. L'étude étant faite à la température de neutralité thermique, l'effet du froid sur le niveau des dépenses énergétiques pouvait être éliminé (Conklin et Heggeness, 1971 ;Planche et Joliff, 1985), et l'augmentation de ces dépenses pouvait être entièrement attribuée à la thermogenèse induite par l'alimentation. A l'âge de 2 jours les échanges gazeux augmentent d'une manière similaire dans les 2 génotypes ( fig.…”

Development of homeothermy in infant C3H mice

“…When in the nest, however, young mice and rats are able to maintain their body temperature (Tb) within a relatively narrow range of about 33°-37°C, even though Ta may be much lower, depending upon a combination of factors, including heat production, infant huddling, insulation quality of the nest, and maternal behaviors (see Leon, 1986, for a review). During the first 3 weeks of life, pups develop an increasing ability to maintain nest-level Teo when isolated at increasingly lower Tas (see, e.g., Conklin & Heggeness, 1971;Fairfield, 1948;Poczopko, 1961). The transition from a poikilothermic to a homeothermic state is not simple, and it clearly reflects the increasing ability of the infant to maintain a thermal balance between heat production and heat loss, using either physiological or behavioral means.…”

“…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.…”

“…From about 5-13 days of age, there is a marked increase in heat production capability, whether measured directly by calorimetry (see, e.g., Walker, 1967) or indirectly by O2 consumption (see, e.g., Fitzgerald, 1953;Lagerspetz, 1962;Thompson et aI., 1968), followed by the gradual increase to adult levels over the next 2 months. Although it is clear that thermoregulatory capabilities improve during this period, some researchers (e.g., Conklin & Heggeness, 1971) have argued that this improvement is due primarily to the increasing capability to produce body heat, whereas others (e.g., Spiers & Adair, 1986) have attributed it primarily to the increasing ability to prevent heat loss.…”