Variable open-loop gain in the control of thermogenesis in cold-exposed rabbits

• Published in: Journal of applied physiology: respiratory, environmental and exercise physiology Vol. 48; no. 3; p. 495
• Main Author: Stitt, J T
• Format: Journal Article
• Language: English
• Published: United States 01.03.1980
• Subjects: Animals; Body Temperature Regulation; Cold Temperature; Hypothalamus - physiology; Male; Mathematics; Models, Biological; Rabbits
• ISSN: 0161-7567
• DOI: 10.1152/jappl.1980.48.3.495

We have previously demonstrated a multiplicative interaction between mean skin temperature (Tsk) and hypothalamic temperature (Thy) in the control of thermogenesis in cold exposed rabbits. Such a model predicts that open-loop gain will not be constant, but will vary according to the direction and degree of Thy displacements and to the prevailing level of Tsk when Thy is altered. Open-loop gain was calculated from steady-state displacements in body temperature induced by sustained step displacements in Thy. Hypothalamic temperature of rabbits was clamped at various levels ranging from 2 degrees C above to 3 degrees C below normal Thy and the resulting changes in rectal temperature attained at steady state were recorded. Experiments were conducted at ambient temperatures (Ta) of 2 degrees and 15 degrees C. Open-loop gain in response to hypothalamic heating was always greater than that obtained in response to equivalent levels of hypothalamic cooling. Furthermore, at lower levels of Tsk (Ta = 2 degrees C) open-loop gain was greater for all levels of Thy displacement when compared to that measured at higher levels of Tsk (Ta = 15 degrees C).