FACTORS AFFECTING METABOLISM in vittO 113 



increased the glucose consumption, oxygen uptake and lactic acid 

 production to rates similar to tliose calculable from data such as 

 that of Klein and Olsen (1947) in cat brain in vivo following 

 electroshock. Under anaerobic conditions pulses suppressed the 

 formation of lactic acid. The presence of sodium ions at concen- 

 trations above 15 mAf is essential to respiratory response. Below 

 this concentration pulses were without effect on oxygen uptake but 

 still increased lactic acid production (Mcllwain and Gore, 1952). 

 In slices metabolizing glucose under anaerobic conditions electrical 

 pulses caused a loss of the bound acetyl choline of the tissue and, if 

 eserine was included in the saline, a corresponding increase in the 

 free form (Rowsell, 1954). Also, under aerobic conditions the 

 levels of phosphocreatine were decreased from 1-5 /xmoles/g wet wt. 

 to 0-6-0-7jumoles/g wet wt., the levels of inorganic phosphate 

 rising by an equivalent amount of 0-9-1-0/xmoles phosphorus/g 

 wet wt. (Mcllwain and Gore, 1951). Quantities of adenosine 

 triphosphate decreased slightly while those of adenosine diphos- 

 phate increased (Kratzing, 1953). These changes are similar to 

 those found in vivo following electroshock or convulsive activity 

 induced by metrazole and established the validity of the techniques 

 as a means of examining both the effect of different therapeutic 

 agents upon the changed metabolism and also as a means of 

 examining the linkage between an applied impulse and metabolic 

 response in nervous tissue. 



Since changes in phosphocreatine in vivo are known to take 

 place within a few seconds, measurements of changes in response 

 to electrical impulses in vitro were made over similar brief periods. 

 It was found (Fig. 12) that within 5 sec of the application of 

 electrical impulses to slices of guinea pig cerebral cortex, phospho- 

 creatine had decreased from 1-5 /xmoles/g to 0- 6-0- 7 /xmoles/g. 

 The quantity did not decrease further upon continued stimulation 

 and would appear to represent a new equilibrium in the balance 

 between synthesis and degradation in the changed conditions. 

 Impulses of a different type or a different strength and duration 

 produce similar effects but to a different degree. Thus in contrast 

 to the above results obtained using condenser impulses of 10-18 V 

 peak potential and 0-4 msec duration at a frequency of 50 cycles/ 

 sec, Greengard and Mcllwain (1955) using sine wave pulses at 

 2000 cycles/sec and 3-5 V peak potential obtained a final lower 

 level of 1-2 /xmoles/g wet wt. Partial decrease in the quantities of 



