Neurotoxin found in the freshwater bryozoan Lophopodella carteri

Previous studies have shown that fish die in the presence of crushed Lophopodella carteri . However, the mechanism of action was not elucidated. This paper reports that L carteri homogenate contains a neurotoxic component. The presence of neurotoxins was tested by bath applying the L. carteri homogenate to rat hippocampal slices while monitoring neuroactivity in the Schaffer Gollateral-CAl pathway using extracellular recording techniques. The homogenate was neurotoxic with an IC50 = 6 id. for orthodromic responses and an IC 50 = 10 μL for antidromic responses. These data suggest a nonsynaptic mode of action. The neurotoxic component apparently acts as an antagonist as noted by the lack of population spikes. Further, the inhibition was reversible. The neuronal response returned after removing the toxin. Partial purification of the toxin suggests that the toxin is not a protein, but a small molecule similar to bioactive molecules that have been found in some marine Bryozoa.