METABOLISM IN CHANGED CEREBRAL ACTIVITY 47 



barbital anaesthesia. Deep anaesthesia and an accompanying drop 

 in body temperature to 27° was accompanied by a further decrease 

 in phosphate incorporation. Similar results have been reported by 

 Palladin (1955). Analysis of exchange in individual phospholipids 

 during 3 hr thiopentone anaesthesia in the rat, showed that phos- 

 phatidyl choline and phosphatidyl ethanolamine decreased in 

 relative specific activity by 60-70%. Decrease in the diphos- 

 phoinositide fraction was much less, being about 20% (Ansell and 

 Dohman, 1957). Depression of incorporation similar to this has 

 been noted following a dose of the tranquillizing agent chlor- 

 promazine. Wase et al. (1956) found that chlorpromazine at 

 25-50 mg/kg over a period of 24-48 hr, suppressed the quantity of 

 phosphate incorporated into the phospholipids of rat cerebral 

 cortex but was without effect upon or slightly increased the 

 incorporation into the phospholipids of other parts of the brain. 

 On the other hand, Ansell and Dohman (1956) found that over a 

 3 hr exchange period, chlorpromazine administered to the rat at 

 20 mg/kg markedly reduced the exchange of phosphorus into the 

 total phospholipids, phosphatidyl choline, phosphatidyl ethanol- 

 amine and phosphatidyl serine both in whole brain and in the 

 cortex, pons, medulla, white matter and cerebellum. With this 

 dose of chlorpromazine the rats showed no obvious signs of 

 sedation (G. B. Ansell, personal communication). 



Biochemical effects of barbiturate anaesthesia in vivo, in addition 

 to those noted above in relation to glucose metabolism are thus 

 seen to include an increase in the levels of phosphocreatine, an 

 increased radioactivity of phosphorus in adenosine triphosphate, a 

 decreased level of inorganic phosphorus and a decreased exchange 

 of phosphorus into the phospholipids. Discussion of ways in which 

 certain of these various effects may be related is deferred to a later 

 chapter (Chapter 5). 



Hypoglycaemia 



Significant decrease in the levels of blood glucose are consistently 

 accompanied by impaired mental and cerebral function and can 

 result in loss of consciousness. Under these conditions in man, the 

 brain uses oxygen at about half its normal rate (Kety, 1948). Since 

 the oxidation of glucose provides the major energy source of the 

 brain, changes in the amount oxidized might be expected to alter 

 the quantities and rates of metabolism of cerebral phosphates. 



