Presynaptic Inhibition and the Anatomy of Group Ia Afferents

Abstract In 1957, Frank and Fuortes (1957) described depression of group Ia excitatory postsynaptic potentials (EPSPs) in hindlimb extensor motoneurons in the cat when preceded by stimulation of group I afferents in flexor muscle nerves. This depression occurred without any detectable postsynaptic inhibitory postsynaptic potentials (IPSPs) or changes in the motoneuron’s excitability, which seemed to rule out conventional postsynaptic inhibition as it was then understood.