Article du Bulletin
Temperature regulation during wakefulness sleep and hibernation in marmots [Régulation de la température au cours du sommeil chez les marmottes vigiles et hibernantes].
Florant G.L., Turner B.M. & Heller H.C. · 1978 · Am. J. Physiol., regulat., integrat. comp. physiol., 4 (1) : 82-88.
Résumé
La température hypothalamique de seuil et la constante de proportionnalité pour la réponse de chaleur métabolique est examinée chez des animaux, en éveil, pendant le sommeil à ondes lentes, le sommeil paradoxal et l'entrée en hibernation. The threshold hypothalamic temperature and the proportionality constant for the metabolic heat production response were investigated in three euthermic marmots during wakefulness (W), slow-wave sleep (SWS), and paradoxical sleep (PS), and in four marmots during entrances into hibernation. Hypothalamic temperature (Thy) was manipulated with chronically implanted, water-perfused thermodes straddling the hypothalamus. Rate of metabolic heat production (MHP) measured as oxygen consumption, ambient temperature (Ta), and (Thy) were continuously recorded during experiments. Arousal states were defined from recordings of the cortical electro-encephalogram (EEG) and the dorsal neck muscle electromyogram (EMG). The proportionality constant which describes the MHP response to a decrease in Thy. (aMHP) was -l.IO W.kg-1.°C-1 for wakeful euthermic marmots at a Ta of 15°C. During SWS, aMHP of euthermic marmots declined to -0.55 W . kg-1 - °C-1. These same animals showed no metabolic response to Thy's as low as 34.5°C during PS. Manipulations of Thy in animals entering hibernation revealed a continuously declining threshold Thy and aMHPm. When aMHP was expressed as a function of threshold it had a temperature coefficient of 2.l. This relationship extrapolated to the aMHP, value of SWS at a euthermic threshold Thy (37°C). These results suggest that the central nervous regulator of body temperature is continuously operative over the entire range of body temperatures (Tb's) experienced by the hibernator. The fact that values of aMHP obtained during hibernation extrapolate to euthermic SWS values rather than euthermic wakeful values lends credence to the hypothesis that hibernation is an extension of thermoregulatory adjustmens which normally occur during SWS.