Extensor motor neurons of the crayfish abdomen

The somata of five deep extensor motoneurons of the third abdominal ganglion of the crayfish (Procambarus clarkii) were located and identified. The positions of these somata within the ganglion and their distal distribution to muscles have been mapped and were constant. The soma of the extensor inhibitor was noted to touch the soma of the flexor inhibitor. Three of the excitatory neurons were clustered near their exit route. Sensory and cord routes of activation of the extensor motoneurons were also found and were constant from preparation to preparation. Sub threshold recording showed that these motoneurons exhibited radically different types of post synaptic response to stimuli at different sites in the nervous system. No interaction between extensor motoneurons or between the extensor and flexor motoneurons was observed.