Miniature synaptic potentials absent from motoneurons of intact spinal cord

Intracellular recordings were made from lumbar motoneurons of decerebrate, paralyzed frogs with minimal surgical damage to the spinal cord. Detectable spontaneous synaptic activity was absent in most motoneurons, as compared with published in vitro recordings. Lesions of the thoracic cord increased the incidence of small spontaneously occurring potentials. This suggests that spontaneous quantal release of transmitter observed in isolated preparations is a consequence of presynaptic neuronal damage.