218 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



higher, and the meuibrane conductance at the peak of activity (measured 

 by the method of voltage clamp) was appreciably smaller than that of the 

 normal fiber. When the temperature of the narcotized axon was changed 

 from 22°C down to 6°-10°C, the spike height recovered to an almost normal 

 value (90-95%). In such a cold ethanol-sea water solution the threshold 

 membrane depolarization usually became smaller than the normal value 

 at room temperature. The membrane conductance at the peak of activity, 

 however, did not change appreciably when a narcotized axon at room 

 temperature was cooled. At very low temperature (3°-5°C), spontaneous 

 firing of impulses was observed in these axons. A similar counteracting ef- 



NORMAL 

 SEA-WATER 



22*C 



3% ETHANOL SEA-WATER 

 22*C ICC 5*C 



SPONTANEOUS 

 FIRING 



Fig. 10. Effects of temperature upon the spike amplitude and tlie tliieshold of a 

 lightly narcotized squid giant axon. The lower records of the three columns at left 

 give a measure of the intensity of membrane current used for threshold excitation. 

 The change in the membrane potential caused by pulses of opposite polarity is also 

 indicated. The effects observed were perfectly reversible. Time marking, 0.2 msec. 



feet of cooling was seen with a 5% ethanol-sea water solution. The effects 

 of temperature on the narcotized fiber are illustrated in figure 10. 



Application of a high pressure was also effective in partially restoring 

 the spike amplitude reduced by ethanol. The threshold membrane poten- 

 tial and the membrane conductance have not yet been investigated under 

 these conditions. 



The effect of temperature and pressure upon the giant axon under 

 ethanol suggests that the action of narcotics upon the axon is analogous 

 to that upon such biochemical systems as the bioluminescent (33). In the 

 bioluminescent system the inhibitory effects of such narcotics as ethanol 

 and urethane can be opposed by pressure. A further investigation into 

 this problem of interaction among narcosis, temperature changes and ap- 

 plication of high i)ressure may throw new light into the mechanism of ac- 

 tion potential production. 



