RESPONSES OF DEAFFERENTED SPINAL NEURONES TO CORTICOSPINAL IMPULSES

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Abstract
In 22 cats at various periods after aseptic intradural section of L3 to S3 posterior nerve roots, decerebration and electrical stimulation of the exposed basis pedunculi was carried out. With the technique employed, faradization of the basis pedunculi immediately following a unilateral section of the posterior nerve roots was ineffectual; 24 hours after deafferentation it produced flexor responses in the intact hind limb but no response in the deafferented extremity. Two to 4 days after section of the posterior nerve roots electrical stimulation of either basis pedunculi was equally effective, while 5-47 days after deafferentation the threshold of excitability to electrical stimulation of the basis pedunculi corresponding to the deafferented hind limb was markedly lowered, the flexor contractions of the deafferented extremity took place after a shorter latent period than those of the intact limb, and were maintained for considerable periods of time after the cessation of the stimulation. It was concluded that section of the posterior nerve roots increases the excitability of the deafferented spinal neurones to nerve impulses reaching them via the corticospinal tract, this taking place after an initial depression of spinal activity.

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