Propriospinal control of interneurons in spinal reflex pathways from tendon organs in the cat

After chronic hemisection at C3, stimulation of propriospinal fibers in the dorsal quadrant at Th 10 facilitated disynaptic PSPs from Ib afferents in hindlimb motoneurons. Recording from interneurons monosynaptically activated from group I muscle afferents, and of extracellular focal synaptic potentials around them, revealed monosynaptic EPSPs from long propriospinal neurons. It is suggested that propriospinal neurons originating in the forelimb segments have direct excitatory connexions with inter-neurons of Ib reflex pathways to hindlimb motoneurons.