Journal of Neuroscience, Vol 4, 1745-1753, Copyright © 1984 by Society for Neuroscience
Physiological evidence for specificity of synaptic connections between individual sensory and motor neurons in the brachial spinal cord of the bullfrog
JW Lichtman and E Frank
We have studied synaptic connections between individual stretch- sensitive
muscle afferents and motoneurons in the brachial spinal cord of bullfrogs.
Sensory afferents from a given head of the triceps brachii muscle
preferentially innervate motoneurons that project to the same muscle head.
This preference is characterized in two ways: each class of sensory axon
innervates a greater proportion of corresponding motoneurons than of
motoneurons projecting to synergistic or unrelated muscles, and the
synaptic potentials in these corresponding motoneurons are motoneurons that
project to the same muscle head. This preference is characterized in two
ways: each class of sensory axon innervates a greater proportion of
corresponding motoneurons than of motoneurons projecting to synergistic or
unrelated muscles, and the synaptic potentials in these corresponding
motoneurons are of larger amplitude. A novel feature of these experiments
is that even the smallest averaged synaptic potential is several times
larger than the noise level. These smallest synaptic potentials thus
represent the smallest synaptic interaction between a sensory and motor
cell, and they could be the physiological correlate of a single sensory
bouton on a motoneuronal dendrite.