Experimental characterization and applications of an anesthetized animal model for thermoregulatory investigations

In the study of mechanisms of thermoregulation conscious animals are used and in most cases the conscious animal is the preferred choice. In some investigations however an anesthetized animal may be the model necessary for the practical purposes of the experimental design. We have developed, tested, and used an urethane anesthetized animal as a model in thermoregulatory investigations. Experiments have been completed in which we have shown that the adult male rat when anesthetized to a surgical level with urethane (1.5 gm/kg) cannot maintain its body temperature and becomes "poikilothermic-like". By providing a steady level of heat to the animal, body temperature can be stabilized for long periods of time at any basal level. This unique feature is not possible in conscious animals. Although apparently poikilothermic, these anesthetized animals respond with a dose-dependent fever to pyrogenic agents such as bacterial pyrogen, interleukin, and prostaglandin. Accompanying these fevers are physiological changes characteristic of fever including increases in arterial and central venous blood pressure, heart rate, oxygen consumption and shivering all of which are similar to the changes which occur in conscious animals. We have used this model for investigations on intracranial pressure, fever suppression and enhancement, application and recovery (for assay) of neuro-transmitters to and from specific brain loci, microdialysis, osmotic stimulation, and electrophysiological stimulation and recording.