Neural Organization and Evolution of Thermal Regulation in Mammals

Abstract

This article proposes a modification of the currently accepted view of the central neural integration of body temperature. In place of a single integrator with multiple inputs and outputs, the new model includes as many integrators as there are thermoregulatory responses. Futhermore, these integrators are postulated to be represented at many levels of the nervous system, with each level facilitated or inhibited by levels above and below. The purpose of such a complicated arrangement is to achieve finer and finer control over body temperature. A consideration of how endothermy might have evolved, with originally nonthermally related responses gradually coming under thermal control, makes such a brain organization highly reasonable.

Effect of Lesions of the Ventrolateral Preoptic Nucleus on NREM and REM Sleep

“…In addition, the rats with ventromedial preoptic lesions showed a significant increase in the variance of body temperature compared with that of VLPO-lesioned animals (variance for body temperature in animals with ventromedial preoptic lesions was 6.7 Ϯ 0.12.; variance for the animals with VLPO lesions was 1.10 Ϯ 0.05; p Ͻ 0.001 by t test). We characterize this combination of deficits as a loss of fine tuning of body temperature, similar to the description of Satinoff (1978) in animals with somewhat larger medial preoptic lesions.…”

“…Because the medial preoptic area adjacent to the VLPO plays an important role in thermoregulation (for review, see Satinoff, 1978), we prepared a second group of animals in which we monitored body temperature as well as sleep behavior after preoptic lesions. In addition, we explored the persistence of the changes in sleep and body temperature after preoptic lesions for 3 weeks in a group of 15 additional rats with ibotenic lesions directed at the VLPO, a group of 5 rats with lesions directed at the ventromedial preoptic nucleus, and a group of 6 control rats that received injections of saline into the VLPO region.…”

Brain and Body Hyperthermia Associated with Heroin Self-Administration in Rats

“…Although it is generally assumed that brain temperature is a strictly regulated homeostatic variable with a range of fluctuations more restricted than those of body temperature (Satinoff, 1978;Bullock et al, 2001), relatively large increases in brain temperature (1.0 -2.0°C) have been found in animals exposed to various biologically significant stimuli or engaged in different behaviors. Temperature in different brain structures increases during exploration of new environment, treadmill running and swimming (Moser et al, 1993), feeding (Abrams and Hammel, 1964), and handling by an experimenter (Delgado and Hanai, 1966).…”

Homeostasis: Beyond Curt Richter

“…In physiological regulation, the term is used metaphorically to indicate that a system operates "as if" there was an engineering type of set-point or reference signal, and this analogy can be misleading (Berridge 2004;Gordon et al 2001). Physiologically plausible models that give regulated systems the appearance of a set-point propose that there are thresholds for activating homeostatic responses and that they exist within hierarchically arranged, and possibly interacting, physiological control systems (Bligh 1998;Bligh 2006;Brengelmann & Savage 1997;Kanosue et al 1997;Romanovsky 2004;Satinoff 1978). When intact animals encounter naturally occurring homeostatic challenges, it is typical to find that physiological responses and motivated behaviors are activated in a coordinated manner to defend a regulated variable (Cabanac 2006).…”