io8 



M. A. ROTHENBERG 



VOL. 4 (1950) 



a given solution cannot be used for a prolonged period of time. The results presented 

 were obtained with fresh eserine solutions. Although there is a marked increase in Na 

 exchange, the effect of eserine is not as large as that obtained with DFP. 



4. Cocaine and Na exchange. The effects of cocaine in 0.005 M in sea water have been 

 studied using 0.13 M Na^^Cl + 0.39 M Na^^Cl in the bathing fluid. Nerves were exposed 

 to this solution for 30 min. The results are reported in Table IX. No decrease in mem- 

 brane permeability is evident from the data. The Na exchange amounted to 11. 2 milli- 

 moles/ioo g (average of six nerves). Again assuming a fibre diameter of 500 /i, this would 

 correspond to a rate of Na exchange of 4.6-10"^ mole/cm^/min, a slight increase com- 

 pared with the control. 



TABLE IX 



EFFECT OF COCAINE ON THE RATE OF PENETRATION OF Na 



Nerves exposed to 0.005 M cocaine in sea water containing 0.39 M Na^^Cl + 0.13 M Na^^Cl. S^ and 

 S, = standards. 



5. Effect of X-ray irradiation. The effects of high intensity X-ray irradiation on the 

 membrane permeability to Na was studied. Nerves were irradiated with 50000 R and 

 125000 R while immersed in a shallow dish containing natural sea water (water layer 

 about 5 mm thick). Immediately after irradiation, the nerves were transferred to 

 artificial sea water containing 0.39 M Na^^Cl + 0.13 M Na^^Cl. After 30 min exposure to 

 sea water the nerves were analysed. Only those nerves which still exhibited normal 

 conduction upon stimulation were used. The results are given in Table X. 



In the axoplasm of nerves irradiated with 125000 R, an average value of 14.1 

 miUimoles/ioo g was found (average of seven values). This corresponds to a penetration 

 of 5.9-10"^ mole/cm^/min. Consequently, the rate of penetration had markedly increased. 

 The findings suggest that irradiation had strongly increased the permeability. 



Irradiation with 50000 R gave an average value of 10.9 millimoles Na/ioo g (average 

 of eight nerves). This corresponds to a rate of penetration of Na of 4.7-10""^ mole/cm^/ 

 min. The increase in the rate of penetration is relatively small but appears significant, 

 especially in connection with the high increase observed with the larger dose of irra- 

 diation. It may be noted that the effect was obtained immediately after irradiation. 



References p. 114. 



