Journal of Neurophysiology, Vol 39, Issue 3 474-483, Copyright © 1976 by APS
Evidence for electrotonic coupling between frog motoneurons in the in situ spinal cord
P. C. Magherini and W. Precht
A recurrent EPSP was observed on antidromic stimulation of motoneurons in
the in situ spinal cord of Rana temporaria and R. esculenta at 20-22C. The
EPSP was finely graded and not refractory following full or partial
antidromic spike components in a given neuron. The EPSP amplitude varied in
parallel with the antidromic field potential under different conditions,
suggesting transmission of the EPSP to the recorded motoneuron depended on
invasion of the somadendritic membrane or neighboring motoneurons by the
antidromic spike. The latency of the EPSP with respect to antidromic
invasion of the local motoneuron pool was too short for the EPSP to be
mediated by chemical transmission. It was concluded the EPSP was
electrically transmitted between the somadendritic membranes of the
motoneurons. Under certain conditions, the EPSP magnitude could be made to
vary with membrane potential in a direction opposite to that expected from
a chemical EPSP. Dendritic spikes were sometimes associated with the EPSP.
