TY - JOUR

T1 - Oscillatory interaction between dorsal root excitability and dorsal root potentials in the spinal cord of the turtle

AU - Delgado-Lezama, R

AU - Perrier, J F

AU - Hounsgaard, J

PY - 1999/1/1

Y1 - 1999/1/1

N2 - The response to dorsal root stimulation, at one to two times threshold, was investigated in the isolated cervical enlargement of the turtle spinal cord. At frequencies near 10 Hz the synaptic response in motoneurons and the cord dorsum potential, after an initial lag time, oscillated in amplitude with a period of more than 1 s. The mono- and polysynaptyic postsynaptic response in motoneurons, the pre- and postsynaptic component of the cord dorsum potential and the dorsal root potential oscillated in synchrony. These oscillations were only observed with stimulus frequencies in the range 9-11 Hz. The oscillating response could only be evoked from stimulus sites to which dorsal root potentials were conducted from the spinal cord (2-3 mm). At more distant stimulus sites cyclic variations in amplitude of the cord dorsum potential and the synaptic response in motoneurons were not observed. During an oscillating spinal response to a stimulus train in one dorsal root filament, the response evoked by a stimulus in another short filament (2-3 mm) from the same root varied in amplitude with the induced oscillation. The spinal response to a stimulus in a longer filament (i.e. more than 3 mm) did not oscillate. It is argued that the oscillating responses described rely on interactions between distributed elements rather than on unit oscillators. We also show that primary afferent transmission is unaffected by the substantial variations in dorsal root potentials during oscillations.

AB - The response to dorsal root stimulation, at one to two times threshold, was investigated in the isolated cervical enlargement of the turtle spinal cord. At frequencies near 10 Hz the synaptic response in motoneurons and the cord dorsum potential, after an initial lag time, oscillated in amplitude with a period of more than 1 s. The mono- and polysynaptyic postsynaptic response in motoneurons, the pre- and postsynaptic component of the cord dorsum potential and the dorsal root potential oscillated in synchrony. These oscillations were only observed with stimulus frequencies in the range 9-11 Hz. The oscillating response could only be evoked from stimulus sites to which dorsal root potentials were conducted from the spinal cord (2-3 mm). At more distant stimulus sites cyclic variations in amplitude of the cord dorsum potential and the synaptic response in motoneurons were not observed. During an oscillating spinal response to a stimulus train in one dorsal root filament, the response evoked by a stimulus in another short filament (2-3 mm) from the same root varied in amplitude with the induced oscillation. The spinal response to a stimulus in a longer filament (i.e. more than 3 mm) did not oscillate. It is argued that the oscillating responses described rely on interactions between distributed elements rather than on unit oscillators. We also show that primary afferent transmission is unaffected by the substantial variations in dorsal root potentials during oscillations.

KW - 6-Cyano-7-nitroquinoxaline-2,3-dione

KW - Animals

KW - Bicuculline

KW - Electric Stimulation

KW - Electrophysiology

KW - Excitatory Amino Acid Antagonists

KW - GABA Antagonists

KW - Membrane Potentials

KW - Motor Neurons

KW - Patch-Clamp Techniques

KW - Receptors, Presynaptic

KW - Spinal Nerve Roots

KW - Turtles

KW - Valine

M3 - Journal article

C2 - 10465457

VL - 93

SP - 731

EP - 739

JO - Neuroscience

JF - Neuroscience

SN - 0306-4522

IS - 2

ER -