TEMPERATURE

Temperature regulation (or thermoregulation) can be defined as the control of the temperature(s) of a body under finite environmental conditions. Regulation is achieved by controlling heat gain and heat loss between the body and the environment through the utilization of autonomic and behavioral mechanisms. Birds and mammals have evolved a battery of behavioral and autonomic outputs to regulate their core body temperatures within narrow limits when subjected to a wide range of ambient temperatures (Prosser and heath, 1991). The system achieves a fine degree of control by utilizing the functions of other organ systems for its motor outputs: the respiratory and digestive systems (e.g. salivary glands in rodents) for evaporation, the cardiovascular system for skin temperature, and skeletal muscle for shivering and behavioral thermoregulatory responses. In rodents, the more important structure involved in thermoregulatory function is the tail, which serves as a heat-loss organ.

Basic empirical observations mixed with religious dogma were used to explain thermoregulatory phenomena in humans until late in the seventeenth century. It was not until the late eighteenth century that modern theories of thermoregulation began to take shape. Lavoisier made some of the first measurements of heat loss in a rat, using a crude, albeit accurate,... [more]

Temperature regulation (or thermoregulation) can be defined as the control of the temperature(s) of a body under finite environmental conditions. Regulation is achieved by controlling heat gain and heat loss between the body and the environment through the utilization of autonomic and behavioral mechanisms. Birds and mammals have evolved a battery of behavioral and autonomic outputs to regulate their core body temperatures within narrow limits when subjected to a wide range of ambient temperatures (Prosser and heath, 1991). The system achieves a fine degree of control by utilizing the functions of other organ systems for its motor outputs: the respiratory and digestive systems (e.g. salivary glands in rodents) for evaporation, the cardiovascular system for skin temperature, and skeletal muscle for shivering and behavioral thermoregulatory responses. In rodents, the more important structure involved in thermoregulatory function is the tail, which serves as a heat-loss organ.

Basic empirical observations mixed with religious dogma were used to explain thermoregulatory phenomena in humans until late in the seventeenth century. It was not until the late eighteenth century that modern theories of thermoregulation began to take shape. Lavoisier made some of the first measurements of heat loss in a rat, using a crude, albeit accurate, ice-bath calorimeter. In the early 1800s, measurements of body temperature and cold resistance in various species of mammals and birds were undertaken. The development of the clinical thermometer by Allbutt in 1867 spurred research on fever and other thermoregulatory processes. Detailed monographs on the temperature regulation of the laboratory rat had been published by the 1930s (e.g. Benedict and MacLead, 1929). One of the most exciting areas of investigation into temperature regulation during the first half of the twentieth century was the search for the central nervous system (CNS) loci involved in the control of body temperature. Researchers such as Bazett, Ranson, and Magoun in the 1930s were instrumental in developing the concept of the anterior/posterior hypothalamus as the key regulatory site for control of body temperature.

Manipulating the output of the thermoregulatory system (e.g. raising or lowering the core temperature) has been and will continue to be crucial aspect of various surgical and therapeutic procedures. For example, without the advantage of hypothermia to lower the body’s oxygen demand, it would be impossible to perform many of today’s common surgical procedures on the heart and brain. Forced elevations and reductions in body temperature have proved to be extremely beneficial in treating some maladies, including some types of cancer and trauma to the CNS. Moreover, the efficacy and toxicity of drugs and other chemicals agents can be markedly altered by changes in body temperature. This point is extremely important to be considered in pharmacological or behavioral studies using rodents, because their body temperatures can change relatively quickly when subjected to a variety of experimental manipulations, stresses and trauma. Along with blood pressure measurements, body temperature is the most commonly measured physiological parameters.

EXPERIMENTAL TESTS