[Polysynaptic effects in neurons of the cervical portion of the cat spinal cord induced by activation of long propriospinal pathways].

Effects evoked in cervical moto- and interneurons by stimulation of lateral (LF) and ventral (VF) funicles at low thoracic level were studied in anaesthetized cats; degeneration of descending supraspinal fibres was provided by preliminary cord sections. LF and (or) VF stimulation evoked PSPs (usually mixed) in 57 of 90 studied motoneurons. Monosynaptic EPSPs were "primary" actions in 9 motoneurons while poly(di)-synaptic EPSPs or IPSPs--in the rest. Intensity of excitatory synaptic action on motoneurons of proximal muscles was substantially higher than on "distal" ones. LF and VF stimulation excited interneurons localized in the ventral quadrant and had no action on interneurons situated more dorsally. The effects studied are suggested to be mainly a result of activation of long proporiospinal fibres ascending via LF and VF to the cervical enlargement; certain part of reactions is supposed to be transmitted via collaterals of descending propriospinal fibres to the cervical neurons.