CHAPTER 2 



METABOLISM UNDER CONDITIONS 

 OF CHANGED ACTIVITY 



In the previous chapter the nature of the phosphate derivatives 

 present in brain and their relative rates of exchange of phosphorus 

 were discussed. The problem of assessing the significance of such 

 exchange, or of the presence of a particular phosphate, as it relates 

 to the functioning of the brain can be approached by altering the 

 normal function and determining how this affects phosphate 

 metabolism. Techniques have been developed and exist for 

 experimental studies of this type and have provided the bulk of the 

 available knowledge. On the other hand study of the changes 

 taking place in brain metabolism during the period in which it is 

 developing and signs of its co-ordinated functioning are appearing 

 in the whole animal also offers a particularly suitable approach. 

 This latter type of study, though not yet as extensive as might be 

 wished, has provided much interesting information and will be 

 considered first. An extended discussion upon the developmental 

 aspects of cerebral metabolism and function has already appeared 

 (Symposium, 1955). 



Phosphates During Development 



Acid-soluble Phosphates 



The development of the brain may be conveniently divided into 

 four stages (see Mcllwain, 1959). The first stage is chiefly 

 characterized by a marked increase in the number of cells. In the 

 mouse, rat or cat this period lasts until birth or shortly afterwards, 

 whereas in the guinea pig or man it is largely complete after two- 

 thirds of the gestation period. During this stage the brain is 

 electrically silent (Hill, 1955; Grain, 1952; Libet et al, 1941; 

 Flexner et al., 1950) and either does not respond or responds only 

 slightly to stimulation, for example when strychnine is applied to 

 the cortex. The second stage is characterized by the growth of 



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