RESUMEN
The experimental evidence on the behavioral state-dependent compartmentalization of temperature in the central nervous system of three homeothermic species has been reviewed to address the question of how selective brain cooling influences hypothalamic temperature regulation.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Retroalimentación/fisiología , Hipotálamo/fisiología , Sueño/fisiología , Vigilia/fisiología , Animales , Relojes Biológicos/fisiología , Circulación Cerebrovascular/fisiología , Frío , Humanos , Hipotálamo/citología , Vías Nerviosas/citología , Vías Nerviosas/fisiología , Neuronas/citología , Neuronas/fisiología , Termorreceptores/citología , Termorreceptores/fisiologíaRESUMEN
In cats, the behavioral state-dependent negative correlation of the pontine-hypothalamic temperature difference, an indicator of selective brain cooling, with the hypothalamic-ear pinna temperature difference, which is an indicator of heat loss from the heat exchangers of the head, is suppressed after bilateral common carotid ligature. Behavioral state-dependent selective brain cooling may underlie a thermal feedback mechanism differentiating the relative influences of hypothalamic and extra-hypothalamic thermoreceptors on the thermoregulatory system during quiet wakefulness and NREM sleep.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Ritmo Circadiano/fisiología , Hipotálamo/fisiología , Sueño REM/fisiología , Vigilia/fisiología , Animales , Conducta Animal/fisiología , Temperatura Corporal/fisiología , Arterias Carótidas/fisiología , Gatos , Círculo Arterial Cerebral/fisiología , Frío , Hipotálamo/irrigación sanguínea , MasculinoRESUMEN
The role of cutaneous and respiratory heat loss for selective brain cooling in different species is discussed and new experimental results from a comparative study are summarized. In three species (cat, rabbit and rat) the difference between pontine and hypothalamic temperatures was studied as a function of head heat exchanger vasomotion appraised by the difference between hypothalamic and ear pinna (cats and rabbits) or nasal mucosa (rats) temperatures during the behavioral states of wakefulness and slow wave sleep at an ambient temperature of 24+/-1 degrees C. The results show that: (i) the pontine-hypothalamic temperature difference is an useful indicator of selective brain cooling since it is positive and inversely correlated with the hypothalamic-ear pinna temperature difference in cats and rabbits and with the hypothalamic-nasal mucosa temperature difference in rats; (ii) respiratory heat loss prevails quantitatively over cutaneous heat loss in maintaining this difference.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Hipotálamo/fisiología , Puente/fisiología , Respiración , Fenómenos Fisiológicos de la Piel , Animales , Temperatura Corporal , Encéfalo/fisiología , Gatos , Oído Externo/fisiología , Conejos , RatasRESUMEN
The mechanisms underlying hypothalamic temperature (Thy) changes across the ultradian wake-sleep cycle were analyzed in cats chronically implanted with EEG and EMG electrodes, and transducers that measured Thy and pontine temperature (Tp). The influence of artificially induced changes in (i) systemic blood temperature, (ii) heat loss from the specific heat exchangers of the head, and (iii) carotid artery occlusion, on Thy, Tp and ear pinna temperature (Ts) during waking (W), synchronized sleep (SS) and desynchronized sleep (DS) were assessed in animals maintained in a thermoneutral environment. The results show that the decrease in Thy during SS is dependent on increased heat loss from heat exchangers (ear pinna), whereas the increase in Thy during DS is due to an alteration in the arterial blood perfusion of the circle of Willis receiving an increased supply of warm vertebral blood that replaces a decrease in supply of cool carotid blood.