Blocking of the impulse and depression of the receptor potential by tetrodotoxin in non-myelinated nerve terminals in pacinian corpuscles.

1. The effect of tetrodotoxin on the impulse and the receptor potential of the non-myelinated nerve terminal in Pacinian corpuscles has been investigated.2. Tetrodotoxin at a concentration of 1 x 10(-7) g/ml. raises the threshold for initiating an impulse at the terminal. 5 x 10(-7) g/ml. tetrodotoxin blocks the initiation of impulses.3. The receptor potential magnitude is reduced to about 60% of the control value by 5 x 10(-7) g/ml. tetrodotoxin within 30-60 min and maintains this value for a logn time. The amount of the maximum reduction in the receptor potential by 1 x 10(-6) and 2 x 10(-6) g/ml. tetrodotoxin is not significantly greater than the one by 5 x 10(-7) g/ml. tetrodotoxin.4. No difference in the time constant of the falling phase of the receptor potential was found before and after application of tetrodotoxin.5. The mechanism underlying the generation of the receptor potential has been discussed and the difference of its mechanism from the one concerned with the junctional potential pointed out.