Comparative Study on the Actions of Toxin Extracts from Two Different Puffer Fishes on INa and Respiratory N-M Transmission in the Rat

[Abstract] We performed a comparative study on the effects of toxin extracts prepared from muscle and liver of two different puffer fishes on voltage dependent sodium current (INa), and compared the results with that of tetrodotoxin (TTX). The amount of toxin contained in the muscle or liver expressed as an amount of equipotent TTX differed in the two species (0.11-57.98μg TTX/g tissue). In addition, we observed the effects of TTX or toxin extracts on the twitch contraction evoked by direct muscle stimulation of the rat hemidiaphragm or indirect phrenic nerve stimulations, in an attempt to understand the mechanisms involved in the transmission failure in the respiratory muscles, due to the ingestion of TTX bearing puffers, and found that TTX or toxin extracts preferentially affect motor nerve rather than muscle.