Phase-dependent transmission in the excitatory propriospinal reflex pathway from forelimb afferents to lumbar motoneurones during fictive locomotion.

In high spinal paralyzed cats the effect of forelimb nerve stimulation on hindlimb motoneurones was investigated during fictive locomotion, which was induced by injection of nialamide and L-DOPA. The EPSPs which were evoked by forelimb nerve stimulation in almost all species of hindlimb motoneurones showed a distinct dependence on the phase of the step cycle. In motoneurones to extensor they were only observed during the extension phase, in those to flexors only during the flexion phase. It is assumed that the transmission in the descending propriospinal excitatory reflex pathway is cyclically modulated at the lumbar level.