Direct monosynaptic contacts between type-identified alpha-motoneurons in the cat.

We have examined, at the light microscope level, putative direct synaptic interconnections, via motor axon collaterals, between type-identified triceps surae alpha-motoneurons labeled by intracellular injection of HRP. The results indicate that monosynaptic recurrent contacts can occur between synergist motoneurons (in this case, medial gastrocnemius to soleus, and vice versa), irrespective of motor unit type (type FF to type S, and vice versa).