416 



^A^A^^L-S NEW YORK ACADEMY OF SCIENCES 



h 



-^^Iw* -> "'\L^ V*iv^ -r^Kr 



'■' r 



- v> 



'IJ^ 



Figure 9. Reversibility of action potential and reappearance of cholinesterase in nerves ex- 

 posed for varying periods of time to DFP, 0.013M. 



The nerve whose action potentials are shown in Column 1 was transferred to sea water imme- 

 diately after the action potential was abolished, and washed for one hour. The nerves of Column 

 2 to 4 were kept in DFP for 30', 60', and 90', after the action potential had disappeared, and then 

 washed in sea water. The top line of each column shows the action potential in the untreated 

 nerves. The second line shows the abolition of the response by DFP. The third line shows the 

 degree of recovery after washing the nerve. The reappearance of cholinesterase activity is shown 

 in the vertical bars of the fourth line. The CO2 output is 233, 129, 88.5, and 50 cmm. per 100 

 mgs. per hour. 



covery of the action potential, the smaller is the amount of cholin- 

 esterase activity. Even after complete and irreversible abolition of 

 the action potential, a small amount of enzyme activity may still be 

 detected. The experiments indicate that cholinesterase inhibition by 

 DFP of cold-blooded animals is partly reversible, for a certain period 

 of time. 



This has been confirmed by observations on in vitro inhibition of 

 cholinesterase solution. DFP was added, in two different concentra- 

 tions, 0.1 and 0.5 [xg. per cc, to cholinesterase solution prepared from 

 electric tissue. At the low concentration of DFP, the enzyme solution 



