METABOLISM IN CHANGED CEREBRAL ACTIVITY 



53 



reduces the oxygen requirements of the brain, hypothermia permits 

 the brain to survive under these conditions without a permanent 

 impairment of metabohsm (Ilimwich, 1951). Changes in phos- 

 phates under the two conditions show marked differences (Table 

 9). At 37°, in the rabbit, cerebral ischaemia resulted in a total loss 

 of phosphocreatine and a loss of half the adenosine triphosphate 

 within 5 min. At 26°, half the phosphocreatine was still present 

 after 5-0 min together with 60-70% of the adenosine triphosphate. 



Table 9. — The Effects of Cerebral Ischaemia upon the Quantities 



OF Adenosine Triphosphate, Phosphocreatine and Inorganic 



Phosphate in Brain 



Data from Thorn et al. (1958) and Isselhard ct al. (1959). 



Rabbits; ischaemia was produced by an inflatable cuff placed round 

 the neck. 



Restoration of the normal quantities of the phosphates is apparently 

 rapid and occurs within 10 min of restoring the circulation 

 (Schneider, 1957), though levels of lactate remain high for much 

 longer (Savchenko, 1958). The changes found in cerebral is- 

 chaemia are similar in degree and^ate to those found in anoxia. 

 Taken together they re-emphasize the primary importance of 

 oxygen in the maintenance of adequate levels of energy-rich 

 phosphates in the adult brain. 



In the majority of experiments commented upon above it has 

 been noted (Gurdjian et al, 1949; Stone et al, 1941; Klein and 

 Olsen, 1947; Gurdjian et al, 1944; Thorn et al, 1955) that the 

 onset of anoxia or ischaemia was detectable by changes in the 



