scholarly journals Hypothalamic thermosensitivity in capsaicin-desensitized rats.

1985 ◽  
Vol 363 (1) ◽  
pp. 227-236 ◽  
Author(s):  
M Cormarèche-Leydier ◽  
S G Shimada ◽  
J T Stitt
Keyword(s):  
Hypothalamic Thermosensitivity

Thermoregulatory responses of febrile sheep to spinal and hypothalamic heating

1987 ◽  
Vol 253 (6) ◽  
pp. R868-R876 ◽  
Author(s):  
C. M. Blatteis ◽  
R. Necker ◽  
J. R. Hales ◽  
A. A. Fawcett ◽  
K. Hirata
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
O2 Consumption ◽  
Plateau Phase ◽  
Lower Range ◽  
Ambient Temperatures ◽  
Hypothalamic Thermosensitivity ◽  
The Mean ◽  
Conscious Sheep ◽  
Skin Temperatures

Fever was induced by the intravenous injection of 0.25 microgram/kg of lipopolysaccharide (LPS) from Escherichia coli in eight conscious sheep exposed to ambient temperatures adjusted to the lower range of thermoneutrality. Chronic spinal or hypothalamic thermodes were perfused with water of 44 degrees C for 20 min or for most of the rising phase of fever (100 min of the mean 166 min total rise time). The effects of spinal and hypothalamic heating were identical. Thus, before LPS, spinal or hypothalamic heating did not affect the rate of O2 consumption (VO2) but increased skin blood flow (as indicated by skin temperatures) and elicited panting; therefore rectal temperature (Tre) fell. During fever rise, the already reduced skin blood flow and respiratory rate were not affected by spinal or hypothalamic heating, but the increased VO2 was reduced; consequently, the rise in Tre was attenuated. During the plateau phase of fever, all responses were similar to those seen before LPS. In febrilysis, heating strongly enhanced the operating heat loss mechanisms and, hence, augmented the fall in Tre. Thus, although the thermoeffectors activated by spinal or hypothalamic heating were modified during the different stages of fever, the effect on body temperature was nearly the same. Therefore there seems to be no change in spinal or hypothalamic thermosensitivity during fever in sheep.

Hypothalamic thermosensitivity in an Emu,Dromiceius novae-hollandiae

1982 ◽  
Vol 393 (3) ◽  
pp. 278-280 ◽  
Author(s):  
C. Jessen ◽  
J. R. S. Hales ◽  
G. S. Molyneux
Keyword(s):  
Hypothalamic Thermosensitivity

Thermal control of respiratory evaporative heat loss in exercising dogs

1980 ◽  
Vol 49 (6) ◽  
pp. 979-984 ◽  
Author(s):  
J. B. Mercer ◽  
C. Jessen
Keyword(s):  
Heat Loss ◽  
Thermal Control ◽  
Body Core Temperature ◽  
Threshold Temperature ◽  
Evaporative Heat Loss ◽  
Hypothalamic Temperature ◽  
Body Core ◽  
Hypothalamic Thermosensitivity ◽  
Total Body ◽  
Heat Exchanges

Experiments were carried out to determine whether respiratory evaporative heat loss (REHL) in exercising dogs is entirely under thermal control or whether a nonthermal input is additionally involved. To determine body core thermosensitivity, hypothalamic perfusion thermodes and intravascular heat exchanges were chronically implanted in the animals. This allowed the temperature of these two areas to be independently manipulated. At 30 degrees C air temperature, REHL was measured in three dogs during rest or while running on a treadmill (6 km . h-1, 0 degree gradient). During exercise, the threshold temperature was lowered by 9 degrees C, and the slope of the heat-loss response was reduced to one-third as compared with rest when hypothalamic temperature alone was clamped at various levels between 30 degrees and 42 degrees C. However, when extrahypothalamic body core temperature was additionally clamped, the decrease in threshold during exercise was reduced to 0.43 degrees C, while the slope of the response was identical to that during rest. The results suggest that by taking account of total body core thermosensitivity, instead of hypothalamic thermosensitivity, the alleged role of a nonthermal input is greatly reduced. In addition, the results showed that the major pat of central thermosensitivity must be attributed to the extrahypothalamic body core.

Sleep and hypometabolism

1988 ◽  
Vol 66 (1) ◽  
pp. 61-69 ◽  
Author(s):  
H. Craig Heller
Keyword(s):  
Natural Selection ◽  
Slow Wave Sleep ◽  
Physiological Mechanism ◽  
Rapid Eye Movement Sleep ◽  
Acid Base Balance ◽  
Acid Base ◽  
Regulation Of Breathing ◽  
Hypothalamic Cells ◽  
Base Balance ◽  
Hypothalamic Thermosensitivity

Metabolic rate (MR) of endotherms is lower during sleep than quiet wakefulness (W), largely as a result of a regulated lowering of body temperature (Tb) during slow-wave sleep (SWS). In mammals this decrease in regulated Tb is evidenced by a lowered hypothalamic thermosensitivity. In avian thermoregulatory systems spinal thermosensitivity is lower in SWS than in W. In rapid eye movement sleep (REMS) there is a severe inhibition of the thermoregulatory systems. Hypothalamic cells that are thermosensitive during W become less so during SWS and become totally insensitive to temperature during REMS. The adjustments in thermoregulatory systems of endotherms that result in lower Tb and MR during SWS have been shaped by natural selection in different species to produce a variety of adaptations for energy conservation. Bouts of torpor, hibernation, or nocturnal hypothermia consist mostly of SWS, and these states involve a downward resetting of hypothalamic thermosensitivity in mammals and spinal thermosensitivity in birds. A physiological mechanism underlying this change in regulation of Tb may be related to the regulation of breathing and acid–base balance. Retention of CO2 occurs at the onset of sleep, shallow torpor, and hibernation and release of excess CO2 occurs when these states are reversed by arousal. Increased plasma CO2 may have a direct effect on hypothalamic neurons involved in thermoregulation, resulting in a decline in regulated Tb.

CNS regulation of body temperature in euthermic and hibernating marmots (Marmota flaviventris)

1977 ◽  
Vol 232 (5) ◽  
pp. R203-R208 ◽  
Author(s):  
G. L. Florant ◽  
H. C. Heller
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Marmota Flaviventris ◽  
Hypothalamic Temperature ◽  
Proportionality Constant ◽  
Metabolic Heat ◽  
Slow Decline ◽  
Rate Of Oxygen Consumption ◽  
Hypothalamic Thermosensitivity ◽  
Deep Hibernation

Hypothalamic thermosensitivity of marmots was characterized during euthermia and hibernation. Hypothalamic temperature (Thy) was manipulated with chronically implanted, water-perfused thermodes while the animal's rate of oxygen consumption was continuously measured. The threshold Thy for eliciting an increase in metabolic heat production (MHP) and the proportionality constant (alphaMHP) relating rate of MHP to Thy were determined. In four euthermic marmots alphaMHP averaged -1.1 W-kg-1-degrees C-1. During the entrance into hibernation, as body temperature (Tb) declined from 36 to 8 degrees C, the threshold Thy for the MHP response progressively declined and was demonstrable at all times. The Thy of marmots in deep hibernation at an ambient temperature (Ta) of 5 degrees C plateaued near 7.5 degrees C, but threshold Thy for MHP showed a continuous slow decline of 0.2-0.4 degrees C a day, until one day prior to arousal. Proportional regulation of Tb was demonstrable at all times during deep hibernation. The average proportionality constant for the MHP response to hypothalamic cooling during deep hibernation in three marmots was -0.08 W-kg-1-degrees C-1. These results demonstrate that the hypothalamic regulator of Tb is active throughout hibernation and that there are progressive changes in its thermosensitivity.

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