EFFECTS OF STIMULATIONS OF THE PYRAMIDAL TRACT AND STRIATE BODY UPON SPINAL MOTONEURONS

Abstract

1) The influence of stimulations of the striate body, internal capsule and pyramidal decussation upon the spinal activity was studied with cats under the slightest degree of Nembutal anesthesia. Intracellular potential recording from lumbaralpha motoneurons, as well as recording of ventral root electrotonic potentials, were performed in association with brain stimulations and sometimes also with dorsal root stimulations.2) Stimulation of the caudate nucleus and globus pallidus reduced the size of spikes in the contralateral ventral roots discharged as a monosynaptic reflex by dorsal root stimulation. Striatal stimulation in isolation produced a positive ventral root potential.3) Stimulation of the caudate nucleus and globus pallidus induced a train of irregular hyperpolarizing deflections in the membrane potential of the contralateral extensor and flexor motoneurons. These hyperpolarizing deflections, which are considered as IPSP's, abolished a spike discharge in a motoneuron reflexly induced by dorsal root stimulation. Similar, but somewhat less marked changes, with a few exceptional cases of facilitatory effect, were found when putamen was stimulated.4) Stimulation of the internal capsule resulted in a facilitated monosynaptic discharge in the contralateral ventral roots. EPSP's and a consequent spike discharge were found by intracellular recording. Sometimes IPSP was recorded prior to EPSP.5) EPSP and spike potential in spinal motoneurons were resulted from stimulation of the pyramidal decussation.6) Some of the spinal interneurons responded both to dorsal root stimulation and to striated stimulation. Others were found responsive to dorsal root stimulation and stimulation of the internal capsule.