Spatial and temporal facilitation of the dorsal root potential

1974 ◽  
Vol 348 (1) ◽  
pp. 23-31
Author(s):  
�ner Tan
Keyword(s):  
Dorsal Root ◽  
Root Potential

Five Sources of a Dorsal Root Potential: Their Interactions and Origins in the Superficial Dorsal Horn

1997 ◽  
Vol 78 (2) ◽  
pp. 860-871 ◽  
Author(s):  
Patrick D. Wall ◽  
Malcolm Lidierth
Keyword(s):  
Motor Cortex ◽  
Dorsal Horn ◽  
Dorsal Root ◽  
Repetitive Stimulation ◽  
Superficial Dorsal Horn ◽  
Dorsal Horn Neurons ◽  
Dorsal Roots ◽  
Myelinated Fibers ◽  
Root Potential ◽  
Stimulation Of

Wall, Patrick D. and Malcolm Lidierth. Five sources of a dorsal root potential: their interactions and origins in the superficial dorsal horn. J. Neurophysiol. 78: 860–871, 1997. The dorsal root potential (DRP) was measured on the lumbar dorsal roots of urethan anesthetized rats and evoked by stimulation of five separate inputs. In some experiments, the dorsal cord potential was recorded simultaneously. Stimulation of the L3 dorsal root produced a DRP on the L2 dorsal root containing the six components observed in the cat including the prolonged negative wave (DRP V of Lloyd 1952 ). A single shock to the myelinated fibers in the sural nerve produced a DRP on the L6 dorsal root after the arrival in the cord of the afferent volley. The shape of this DRP was similar to that produced by dorsal root stimulation. Repetitive stimulation of the myelinated fibers in the gastrocnemius nerve also produced a prolonged negative DRP on the L6 dorsal root. When a single stimulus (<5 μA; 200 μs) was applied through a microelectrode to the superficial Lissauer Tract (LT) at the border of the L2 and L3 spinal segments, a characteristic prolonged negative DRP (LT-DRP) began on the L2 dorsal root after some 15 ms. Stimulation of the LT evoked DRPs bilaterally. Recordings on nearby dorsal roots showed this DRP to be unaccompanied by stimulation of afferent fibers in those roots. The LT-DRP was unaffected by neonatal capsaicin treatment that destroyed most unmyelinated fibers. Measurements of myelinated fiber terminal excitability to microstimulation showed that the LT-DRP was accompanied by primary afferent depolarization. Repetitive stimulation through a microelectrode in sensorimotor cortex provoked a prolonged and delayed negative DRP (recorded L2–L4). Stimulation in the cortical arm area and recording on cervical dorsal roots showed that the DRP was evoked more from motor areas than sensory areas of cortex. Interactions were observed between the LT-DRP and that evoked from the sural or gastrocnemius nerves or motor cortex. The LT-DRP was inhibited by preceding stimulation of the other three sources but LT stimulation did not inhibit DRPs evoked from sural or gastrocnemius nerves on the L6 dorsal root or from motor cortex on the L3 root. However, LT stimulation did inhibit the DRP evoked by a subsequent Lissaeur tract stimulus. Recordings were made from superficial dorsal horn neurons. Covergence of input from LT sural, and gastrocnemius nerves and cortex was observed. Spike-triggered averaging was used to examine the relationship between the ongoing discharge of superficial dorsal horn neurons and the spontaneous DRP. The discharge of 81% of LT responsive cells was correlated with the DRP.

Intracellular Slow Potential of Dorsal Root Fibers

1956 ◽  
Vol 184 (2) ◽  
pp. 338-344 ◽  
Author(s):  
K. Koketsu
Keyword(s):  
Nerve Fiber ◽  
Dorsal Root ◽  
Surface Membrane ◽  
Conditioning Stimulus ◽  
Spike Potential ◽  
Slow Potential ◽  
Dorsal Root Reflex ◽  
Root Potential ◽  
Increased Strength ◽  
Root Fiber

Intracellular potential changes associated with excitation were recorded from a dorsal root fiber in the funiculus of an isolated spinal cord of a bullfrog or toad. The spike potential of a dorsal root fiber was observed to follow the slow positive (inside) potential. This slow potential was recorded without a spike potential by applying stimuli sub-threshold for the impaled nerve fiber. The size of the slow potential increased gradually with increased strength of dorsal root stimuli, but with no accompanying prolongation of its declining phase. Dorsal root reflex discharges were occasionally superimposed on this slow potential. No summation of the slow potential resulted from two successive supramaximal stimuli. The slow potential induced by a test stimulus showed considerable occlusion even half a second after the conditioning stimulus. The slow positive (inside) potential was also recorded intracellularly by applying antidromic ventral root stimuli. The slow potential recorded here proved to be generated intrinsically by the depolarization of the surface membrane of the impaled nerve fiber. Active depolarization of the membrane of the terminal endings of the dorsal root fiber may spread out electrotonically along the membrane of the nerve fiber and provide this slow potential. The membrane of terminal endings of a single dorsal root fiber may be depolarized secondarily by the activity of other dorsal root fibers or secondary neurons. The relationship between positive deflection of the cord dorsum potential, the dorsal root potential, and the slow potential recorded intracellularly in this experiment has been analyzed.

Specific effects of α-D,L-aminoadipic acid on synaptic transmission in frog spinal cord

1980 ◽  
Vol 58 (6) ◽  
pp. 692-698 ◽  
Author(s):  
Ante L. Padjen ◽  
Peter A. Smith
Keyword(s):  
Amino Acids ◽  
Spinal Cord ◽  
Dorsal Root ◽  
Lateral Column ◽  
Specific Effects ◽  
Acidic Amino Acids ◽  
Frog Spinal Cord ◽  
Gap Technique ◽  
Root Potential ◽  
Sucrose Gap

The sucrose gap technique was employed to investigate both synaptic and amino acid evoked responses from motoneurones or primary afferents of frog spinal cord. α-D,L-Aminoadipic acid (α-D,L-AAD) selectively antagonized responses to acidic amino acids, especially aspartate. The drug was most effective in antagonizing the polysynaptic components of synaptic potentials evoked by dorsal root or lateral column stimulation but had little effect on their monosynaptic components. The ventral root dorsal root potential which is thought to be mediated by a pathway that does not involve acidic amino acids was insensitive to α-D,L-AAD. These data, which were confirmed by intracellular recording from motoneurones, provided further evidence for the role of acidic amino acids in polysynaptic pathways in frog spinal cord.

Heterosynaptic modulation of the dorsal root potential in the turtle spinal cord in vitro

2006 ◽  
Vol 177 (2) ◽  
pp. 275-284 ◽  
Author(s):  
Raúl E. Russo ◽  
Rodolfo Delgado-Lezama ◽  
Jørn Hounsgaard
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Root Potential

A NOTE ON THE TWO COMPONENTS OF THE DORSAL ROOT POTENTIAL

1944 ◽  
Vol 7 (6) ◽  
pp. 327-329 ◽  
Author(s):  
F. T. Dun ◽  
T. P. Feng
Keyword(s):  
Dorsal Root ◽  
Root Potential
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