The inhibitory effects of toxin extracted from muscle or liver of five different 
puffer fishes (hereafter referred as puffer(s)) captured on the Japanese sea 
coast were examined on voltage-dependent sodium current (I(Na)) recorded from 
dissociated single rat hippocampal CA1 neurons. The inhibitory effects estimated 
from IC(50) values of toxin extracts on I(Na) were in the order of Takifugu 
vermicularis > Lagocephalus wheeleri > Canthigaster rivulata > Takifugu rubripes 
> Arothron reticularis from muscle and T. vermicularis > T. rubripes > L. 
wheeleri > A. reticularis > C. rivulata from liver, thereby indicating that the 
amount of toxin in the liver or muscle differs between puffers. In addition, the 
present results indicate that the muscle of T. vermicularis, which is eaten in 
Japan, contains relatively higher amounts of toxin compared to those of T. 
rubripes, also eaten. This observation suggests that caution should be taken 
concerning the maximal edible amount of muscle prepared from T. rubripes.