Tetrodotoxin‐Sensitive action potentials from the brain of the polyclad flatworm, Notoplana acticola

Action potentials recorded intracellularly from the brain of the polyclad flatworm, Notoplana acticola, show reductions in amplitude in the presence of 3.2 × 10−5 M tetrodotoxin. Vibration responder cells and spontaneously active cells were sensitive to tetrodotoxin. One cell was found that did not respond to the toxin. Most brain cells filled with Lucifer Yellow dye were found to be heteropolar multipolar neurones quite unlike those commonly found in other invertebrate ganglia.