44 METABOLISM IN CHANGED CEREBRAL ACTIVITY 



activity. The similar rates of decline noted, w^hether adult or 

 infant rats were chosen, also make it unlikely that the retention of 

 radioactivity is associated specifically with phospholipids which 

 increase rapidly during growth and later form part of more per- 

 manent structures, though it must be noted that studies upon the 

 incorporation of phosphate into specific lipids over these periods 

 have not yet been reported. 



However, factors involved in assessing the decline must include 

 both the initial slow rate of penetration of phosphorus to all parts 

 of the brain and the level of radioactivity found in the acid-soluble 

 phosphates which are presumably the precursors of the phospho- 

 lipid phosphorus. In the mouse, 10 days after injection the specific 

 activity of these phosphates was still 60-65% of that found within 

 6 hr of injection (Dziewiatkowski and Bodian, 1950), a decrease in 

 activity comparable in slowness with that of the phospholipids. 



Effects of A?iaesthesia 



Anaesthesia, as recognized in vivo, is a clinical phenomenon 

 and an analysis of the mechanisms involved as they relate to bio- 

 chemical changes first requires a description of the phenomenon 

 in biochemical terms. To date, such descriptions have been 

 concerned largely with mechanisms involving energy metabolism. 



Anaesthesia, in vivo, is normally accompanied by a marked 

 reduction in the overall rate of cerebral metabolism. Thus, the 

 consumption of oxygen and glucose, the formation of lactic acid 

 and the electrical activity of the cortex are decreased (Himwich, 

 1951). Under these conditions changes have been found both in 

 the quantities and rates of exchange of cerebral phosphates. In the 

 brain of animals anaesthetized with barbiturates and dropped into 

 liquid nitrogen, quantities of phosphocreatine were found to 

 increase while the levels of inorganic phosphate fell (Table 7). 

 Levels of adenosine triphosphate were not affected. However such 

 general effects have not always been noted. Thus, Lin et al. (1958) 

 found no change in the quantities of phosphocreatine if rats were 

 anaesthetized with ether, results similar to those described by 

 Bain (1957). Differences of this type tend to discount suggestions 

 that the anaesthetic merely protects the brain from stimulation 

 during sacrifice. More possibly it indicates a specific effect of 

 barbiturates. Extensive data is lacking but it may perhaps be 

 noted that Doring and Gerlach (1957) also using rats, were unable 



