Effect of a plant-derived spider toxin analogue on crayfish neuromuscular junctions

N-8-Coumaroyl spermidine (N8-CS) is an example of hydroxycinnamic acid - po lyamine conjugates found in certain plants. Because of its structural simil arity to some spider toxins, N8-CS was tested for its ability to block arth ropod neuromuscular synapses. It inhibited chemical synaptic transmission a t crayfish (Procambarus clarkii) neuromuscular junctions, the IC50 being ap proximately 200 mu M. Its effect was at least partially reversed by washing with physiological saline. Joro spider toxin, a structurally similar compo und, also blocked crayfish neuromuscular synapses but its effect was irreve rsible. These results suggest that plant-derived cinnamoyl spermidines migh t have paralytic properties similar to those of spider toxins.