Excitatory connections between spinal motoneurons in the adult rat.
OBJECTIVE
Dendro-dendritic and dendro-somatic projections are common between spinal motoneurons. We attempted to clarify whether there are functional connections through these projections.


METHODS
Motoneurons were antidromically stimulated by the muscle nerve and recorded intracellularly to examine the direct interaction between them after the related dorsal roots had been cut.


RESULTS
Excitatory connections, demonstrated by depolarizing potentials in response to muscle nerve stimulation, were found between motoneurons innervating the same muscle or synergistic muscles, but never between motoneurons innervating antagonistic muscles. These potentials were finely graded in response to a series of increasing stimuli and resistant to high frequency (50Hz) stimulation.


CONCLUSIONS
These results indicate that excitatory connections, with certain specificity of spatial and temporal distribution, occur in the spinal motoneurons. It is also suggested that electrical coupling should be involved in these connections and this mechanism should improve the excitability of the motoneurons in the same column.
Zhou
H
H
Department of Physiology, Institute of Basic Medical Sciences, CAMS & PUMC, Beijing 100005.
Xie
Y
Y
D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation; D006614:Hindlimb / Q000294:innervation*; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D010543:Peroneal Nerve / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology*