GLUCOSE AND OXYGEN UTILIZATION IN SYMPATHETIC GANGLIA 



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POSTSYNAPTIC RESPONSE 



Fig. 1. Effects of anesthetics and of cyanide on the activity increment in rate of 

 oxygen consumption (ordinates) and on the height of the postganglionic action po- 

 tential (abscissae) in excised superior cervical ganglia (rabbit). The preganglionic 

 nerve was stimulated supramaximally about 10 times per second. Both variables are 

 expressed in percent of their values in the absence of experimental substances. (Larra- 

 bee, Ramos, and Biilbring, 1952). 



et al, 1949; Jarcho, 1949; Marshall, 1941 ; Marshall, Woolsey and Bard, 1941). 

 Such selective effects on the activity component of metabolism, if indeed they do 

 occur, might be especially significant in the action of anesthetics on the func- 

 tional capacity of the brain, where normal physiological properties are asso- 

 ciated with a background of continual spontaneous neuronal activity. 



A set of experiments, designed to compare the effects of anesthetics on the 

 activity increment in oxygen uptake with the effects on the neuronal activity 

 itself, are summarized in Fig. 1. Here the number of impulses discharged by 

 a ganglion during repetitive activity is measured by the height of the post- 

 ganglionic action potential. This is depressed in almost exactly the same pro- 

 portion as the increment in oxygen consumption, by each concentration of the 

 anesthetics tested. This raises the question whether the first step in action of 

 the anesthetics is interference with oxidations, or whether the activity is de- 

 pressed by some other mechanism, the decline in rate of oxygen uptake then 

 resulting as cellular activity subsides towards the resting level. This experiment 

 is probably best interpreted on the second basis (i.e., as evidence against a 

 primary disturbance in oxygen metabolism), since there generally seems to be 

 a factor of safety in the chemical reaction systems; moderate oxidative dis- 

 turbances do not in general lead to loss of function, at least not with the ra- 

 pidity revealed in effects of anesthetics. The existence of a factor of safety is 

 confirmed in Figure 1 by the application of cyanide to rabbit ganglia. In this 

 case the activity increment in oxygen consumption was almost completely 

 abolished with relatively little effect on the activity itself. 



The experiments on ganglia just described illustrate a problem in interpreta- 



