EFFECTS OF PYRAMIDAL TRACT STIMULATION ON FORELIMB FLEXOR MOTONEURONSDURING FICTIVE LOCOMOTION IN CATS

To investigate spinal mechanisms of control of locomotion by the pyram idal system, we made intracellular recording from forelimb flexor moto neurons, and analyzed excitatory postsynaptic potentials (EPSPs) evoke d by stimulation of the medullary pyramid during forelimb fictive loco motion in immobilized, decerebrate cats. We observed that (1) pyramida l stimulation evoked disynaptic EPSPs, (2) which were much bigger in t he locomotor state than in the resting state, and that (3) the pyramid al EPSPs were rhythmically modulated, so that the facilitation occurre d in the flexor-active phase. Last-order neurons mediating pyramidal e ffects presumably receive rhythmic input from the spinal locomotor net work. (C) 1997 Elsevier Science Ireland Ltd.