BODY TEMPERATURE AND FOOD AND WATER INTAKE 373 



intake is otherwise completely inhibited (Appleman and Delouche, 1958). 

 The water intake is initially totally inhibited and later markedly reduced 

 during periods of preoptic and anterior hypothalamic cooling (Fig. 10). 



The importance of the preoptic region and anterior hypothalamus for 

 the thermal inhibition of food intake is further indicated by the effect of 

 bilateral lesions in this part of the brain. A goat in which the " heat loss 

 centre " had been destroyed by proton irradiation developed adipsia but 

 continued to eat its normal ration of hay with apparently good appetite, 

 even when its body temperature was raised above 41 °C (Andersson and 

 Larsson, 1961). Rats with corresponding lesions when heat stressed eat 

 twice as much as their controls but drink less water (Hamilton, 1962). 

 Due to the higher food intake the body temperature of the lesioned rats 

 rises two to three degrees centigrade above the controls and may reach 

 lethal threshold. 



Local warming of any part of the central nervous system may act as a 

 nonspecific stimulus ; local cooling, on the other hand, may inhibit all 

 neuronal activity in the close vicinity of the thermodes. Presently the 

 possibility can therefore not be excluded that the alimentary effects of 

 hypothalamic warming and cooling may be more or less nonspecific and 

 not solely due to a stimulation or inactivation of neurons specifically 

 sensitive to heat. Since the " heat loss centre " apparently also controls 

 endocrine factors of importance for intermediary metabolism, the pos- 

 sibility remains that changes in the hormonal status of the animal during 

 preoptic warming and cooling may effect an " appestate " mechanism 

 related to carbohydrate and fat metabolism. 



Nevertheless, taken together, the alimentary effects of anterior hypo- 

 thalamic lesions and those due to hypothalamic warming and cooling 

 indicate that a " thermostatic '' mechanism in Brobeck's (1960) sense really 

 exists. It may, however, mainly serve as an emergency mechanism which 

 prevents additional caloric supply and secures the extra supply of water 

 necessary for urgent heat loss mechanisms, when the body temperature 

 reaches a critically high level. 



REFERENCES 



Anand, B. K. and Brobeck, J. R. 1951. Hypothalamic control of food intake in rats 



and cats. Yale J. Biol. Med. 24, 123-140. 

 Andersen, H. T., Andersson, B. and Gale, C. C. 1962. Central control of cold defense 



mechanisms and the release of " endopyrogen " in the goat. Acta Phvsiol. Scand. 54, 



159-174. 

 Andersson, B. 1952. Polydipsia caused by intrahypothalamic injections of hypertonic 



NaCl-solutions. Experientia 8, 157. 

 Andersson, B., Ekman, L., Gale, C. C. and Sundsten, J. W. 1962a. Activation of 



the thyroid gland by cooling of the pre-optic area in the goat. Acta Phvsiol. Scand. 



54, 191-192. 



