CENTRAL AND PERIPHERAL MECHANISMS 
DR. LIM: The only experiment I have that would suggest such a 
phenomenon is one where we studied exercise in the unanesthetized 
dog. We put the animal on a treadmill which was immersed in a 
water tank, so that he could be cooled during exercise. It appeared 
that such animals shivered as well as panted. Here again this was 
observed in the unanesthetized dog and there may be a conditioned 
reflex involved. 
DR. HENSEL: I think one must be careful with the studies 
during work because there is evidence that work will set the thermo- 
stat to another level. It is not just a rise in the core temperature. 
DR. HEMINGWAY: Anesthetics such as morphine really disturb 
temperature regulation. For example it is possible to get shivering 
and what appeared to be panting at the same time with morphine 
anesthesia. This is such a disturbance caused by the anesthetic. 
I have always felt that temperature threshold values for skin temper- 
ature and rectal temperature and brain temperature under anesthesia 
are quite variable. You can get almost anything you want, depending 
upon the depth of the anesthesia. After giving phenobarbital anes- 
thesia, all these thresholds are depressed, then they come back. 
Shivering comes back first andthethermocutaneous vasomotor res- 
ponse comes back later. However, you are never sure just what the 
anesthetic level is or how much depression has been caused by the 
anesthesia. 
DR. LIM: That is certainly true in short- acting anesthesia, par- 
ticularly amytal, but barbital- sodium is long acting. We have based 
several studies on how the latter affects the blood pressure, res- 
piration, and body temperatures. They all stay fairly constant, and 
within normal range for eight hours or more after a single dose. 
Thus, we thought barbital- sodium was the best preparation for our 
studies because it maintains a steady background. 
DR. HENSEL: Concerning the vasoconstriction during hypothal- 
amic cooling, there is quite a high impairment in the anesthetized as 
compared to the non- anesthetized cat. It can abolish the whole mech- 
anism even during the light anesthesia. I do not know how it is with 
studies of shivering, but this is a difficult problem in circulatory 
studies. 
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