BODY TISSUES 309 



derived from oxidative phosphorylation or Iroui transphosphorylation 

 I'rom phosphocreatine. These high-energy phosphate compounds in- 

 crease slightly during periods of nerve inactivity, although the level 

 remains fairly constant. Respiration increases during periods of stimu- 

 lation to bring about recovery whenever quantities of ATP are needed 

 lor acetylcholine resynthesis. 



The hormones noradrenaline and adrenaline (page 315) occur 

 in the central nervous system and play a role in the sympathetic 

 nervous system similar to that of acetylcholine in the parasympathetic 

 svstem. An amine oxidase occurs in cerebral tissues and limits the 

 action of adrenaline by oxidation to the corresponding aldehyde in a 

 manner analogous to the hydrolysis of acetylcholine by choline esterase 

 in the parasympathetic system. 



The use of specific inhibitors has aided in the study of the effects 



CHo 



I 



CHg 0^ O 



/\ 



CHo ,0 F 

 \ / 

 H— C 



CH3 

 diisopropylfluorophosphate 



of acetylcholine and adrenaline on nerve transmission. Eserine is a 

 reversible inhibitor of choline esterase. Addition to an zn xntro system 

 results in alteration of the action potential; it may be removed from 

 the nerve by washing, with restoration of conduction. Diisopropyl- 

 fluorophosphate is an irreversible inhibitor of choline esterase and of 

 nerve action. Many of the newer organic phosphate insecticides pre- 

 sumably function through this type of inhibition. Ephedrine and 

 benzedrine are amine oxidase inhibitors and thus interfere with the 

 normal enzymatic conversion of adrenaline and noradrenaline. 



