Dorsal Root Potentials evoked by Natural Stimulation of Cutaneous Afferents

Abstract

PRESYNAPTIC inhibition of primary afferent fibres effectively controls the influx of information from the periphery into the spinal cord. In recent systematic investigations of this inhibition (for review, see Eccles¹) electric stimulation of cutaneous and muscle nerves of the hind limb was used. It was found that presynaptic inhibition depresses the excitatory synaptic actions of primary afferent fibres through a prolonged depolarization of their central endings causing a block or reduction of the amplitude of the presynaptic action potential and thus a diminished transmitter output. This depolarization of the central endings is specific to certain recipient afferent fibres. For instance, cutaneous afferents are predominantly depolarized by cutaneous volleys and to a lesser extent by high threshold muscle afferents.