DISINHIBITION IN THE CAT SPINAL CORD

Abstract

Experiments have been conducted in spinal, unanesthetized cats in order to investigate the synaptic mechanism of recurrent facilitation. Changes in the membrane of motoneurons facilitated by antidromic stimuli have been studied by means of intracellular recording and stimulation. In many, but not all, facilitated cells the conditioning volley caused a small depolarization, the recurrent facilitatory potential. Conditioning also increased the magnitude of subthreshold excitatory synaptic potentials and made more effective a stimulus applied through the microelectrode. The recurrent facilitatory potential was consistently reversed or decreased by hyperpolarizing pulses applied through the microelectrode. It is concluded that recurrent facilitation is due to disinhibition of motoneurons.