GLUCOSE AND OXYGEN UTILIZATION IN SYMPATHETIC GANGLIA 91 



Moreover, the very fact of selective action warns against discarding meta- 

 bolic theories merely because indisputably direct metabolic effects of anesthet- 

 ics in appropriate concentrations have not yet been detected. Selective action 

 means effects limited to particular regions. If important metabolic disturbances 

 were localized in restricted critical structures, the changes might well be un- 

 detectable amidst the total metabolism of a whole neuronal aggregate. 



II. Substrates for Oxidation at Rest and in Activity 



The preceding descriptions illustrate some types of experiments that can 

 be performed on sympathetic ganglia, taking advantage of survival of function 

 after excision and the possibility of regulating and measuring the amount of 

 neuronal activity. It is obvious that more could be learned if the number of 

 ways of measuring metabolism were increased. Not only would investigations 

 concerning anesthetics be aided, but so would knowledge of the normal metab- 

 olism of nerve cells, including the changes in chemical reactions accompanying 

 the shift from rest to activity. Moreover, we have found that these ganglia and 

 their related nerves are dependent on an external supply of glucose, in contrast 

 to previous experience with excised peripheral nerve trunks. Thus here may be 

 a particularly favorable opportunity for studying the use of this important 

 substrate. 



Accordingly, we have recently devoted considerable effort to developing and 

 improving methods for measuring metabolism in small ganglia. The rate of 

 oxygen uptake can now be measured in absolute terms, instead of only relative 

 to control states as formerly, while stimulating electrically and recording action 

 potentials. This is done under sterile conditions. Measurements of glucose up- 

 take and lactate production have also been obtained, both at rest and during 

 activity. In addition we are now measuring the rate of ammonia production, 

 as a clue to amino acid metabolism. 



Methods 



Superior cervical ganglia, together with portions of the preganglionic and 

 postganglionic nerves, were excised from anesthetized rats. Wet weights of these 

 preparations were about 1 mg. The preparations were bathed at 35° to 37°C in 

 a bicarbonate-buffered solution previously described (Larrabee and Bronk, 

 1952, Table I, solution D). Under these conditions capacity for axonal conduc- 

 tion and synaptic transmission survived for 12 to 24 hours. 



Oxygen Consumption 



The respirometer used in measuring rate of oxygen consumption was based 

 on the continuous flow principle described by Carlson, Brink and Bronk (1950). 

 In this method a suitably polarized platinum electrode (Davies and Brink, 



