Action of soman on earthworm and its dorsal muscle

The action of soman on earthworm (Eisenia foelida) was found to be quite different from that on leech (Hirudo nipponia). Soman elicited an excitatory effect on both worms and their muscle preparations. In soman solution, leeches always coiled up while earthworms did not. After soman intoxication, the relaxation of muscle after contraction was much quicker in earthworm than in leech. This was thought to be attributed to the rich innervations of inhibitory nerves in earthworm and of excitatory nerves in leech. The effect of soman was greatly reduced on the ChE-deactivated muscle preparations and was more marked in leech than in earthworm. Soman caused a definite but not too strong depressant effect against GABA in this preparation. The authors propose that the earthworm dorsal muscle preparation is a satisfactory model for studying soman.