FURTHER OBSERVATIONS ON CHRONIC DEFICITS OF TEMPERATURE REGULATION PRODUCED IN CATS BY PREOPTIC LESIONS.
NAVAL AIR DEVELOPMENT CENTER JOHNSVILLE PA AEROSPACE MEDICAL RESEARCH DEPT
Pagination or Media Count:
Destruction by electrolysis of a small region extending at least 0.5 mm either side of the midsagittal plane of the preoptic region of the hypothalamus of cats led to sustained, significant decrease of mean daily colonic temperature as long as the animals were undisturbed at ambient temperatures of 19 to 27 C. Exposure of such animals to unfamiliar surroundings, handling, physical restraint, local cooling of the skin, or cold 0 to -5 C ambient temperatures produced a rise in colinic temperature accompanied by palpable shivering, which was absent as long as the animals were undisturbed. When the same animals were subjected to high 40 C ambient temperatures, their previously subnormal colonic temperatures rose to levels higher than those of unoperated control animals similarly exposed, while panting was observed in both. Lesions of the same general region which tended to spare the medial preoptic region were often associated with initial hyperthermia, which sometimes gave way to delayed hypothermia. An initial hypothermia following a bilateral medial preoptic lesion, however, never gave way to delayed hyperthermia. It is therefore suggested that the initial hyperthermia could have been due to inflammatory irritation of the medial preoptic region, and that the subsequent hypothermia was the result of progression of the inflammatory process to the point of destruction of a critical amount of medial preoptic tissue. These findings indicate that the preoptic region of the cats hypothalamus contains structures sensitive to both heat and cold, therefore to changes in blood temperature in either direction. Author
- Anatomy and Physiology