Presynaptic and Postsynaptic Inhibition in the Central Nervous System

　Frank ＆ Fuortes（1957）and Frank（1959）first clearly showed that there were two distinct types of inhibition. Subsequent investigation by our research groups at Canberra has revealed that in the spinal cord a large proportion of the inhibitions is effected by the presynaptic type of inhibition, in which depolarization of excitatory presynatic fibres depresses their synaptic action. In fact it has now been shown that virtually all medullated primary afferent fibres in the spinal cord are depolarized by conditioning volleys with a consequent depression of their synaptic efficacy.