METABOLISM IN CHANGED CEREBRAL ACTIVITY 63 



pholipids by Dawson and Richter (1950^). Mice injected with 

 radiophosphate were placed in a slowly rotating drum for 3 hr 

 during which they showed signs of fear, micturation, defaecation 

 and attempts to escape. The specific radioactivity of the phospho- 

 lipid phosphorus was decreased by an average of 25% of the 

 normal values. No such decrease was detectable in animals which 

 had previously been conditioned to the drum. The statistical 

 significance of the decrease was small (P = OT) but was con- 

 sidered to indicate that the change was a genuine one. 



Experiments of the above type seek to establish changes occur- 

 ring as a result of stimuli which can be regarded as physiological 

 and afford a valuable contribution to the understanding of the role 

 of phosphate metabolism in relation to the activity of the brain. To 

 a considerable extent such changes parallel those found to result 

 from seizure activity suggesting involvement of similar mechanisms 

 which are being stimulated to greater or lesser degrees. Though 

 this is probably an oversimplification it nevertheless provides a 

 starting point from which to continue further studies of cerebral 

 phosphate metabolism as it relates to functional activity. These 

 form the theme of the next chapters. 



Other Factors Affecting Phosphate Metabolism 



Amongst other factors affecting the metabolism of cerebral 

 phosphates one of the more prominent is a lesion due either to 

 surgical treatment, to injury or to the presence of tumorous tissue. 

 The increased uptake of radioactive phosphate into lesions induced 

 experimentally or into a tumour is most probably due to a break- 

 down of the blood-brain barrier (see Bakay, 1955, for extensive 

 discussion). Thus in tumorous tissue or tissue in which surgical 

 lesions had been made, the uptake of intravenously administered 

 radioactive phosphate was extremely rapid and occurred solely in 

 the acid-soluble phosphates (Stern and Marshall, 1951). This 

 might perhaps be expected if permeability factors were involved. 

 However, injury to one part of the cortex also affects the meta- 

 bolism of other parts of the cortex. In cats, lesions produced by 

 freezing portions of the exposed cortex with liquid air, and subse- 

 quent removal, resulted in changes in phosphate levels in portions 

 of the cortex which were at a distance from the point of injury 

 (Stone et al.^ 1941). Lactic acid levels were increased while levels 



