Glycinergic inhibition in the turtle spinal cord regulates the intensity and pattern of fictive flexion reflex motor output.

Application of strychnine sulfate (10-50 mu M) to the anterior hindlimb enlargement of the turtle spinal cord increased the amplitude of the ipsilateral fictive flexion reflex and revealed a contralateral (crossed) fictive flexion reflex response to cutaneous stimulation of the foot. Strychnine abolished the crossed inhibition of fictive flexion reflex that was normally evoked by contralateral foot stimulation, unmasking the crossed excitation. Our observations are consistent with the hypothesis that intraspinal inhibition mediated by strychnine-sensitive glycine receptors regulates the amplitude of fictive flexion reflex motor output and confines the response to the appropriate neural pathways.