Spinal Border Cells Research Articles

Direct and indirect activation of nerve cells by electrical pulses applied extracellularly.

1. The mode of activation of nerve cells by extracellular stimuli was investigated while recording from a selected cell with one electrode, and applying current pulses around this cell with another electrode. The analysis was done on motoneurones and on spinal border cells from lower lumbar segments in the cat. 2. Directly evoked action potentials were defined by their appearance in an all-or-none fashion with stable latencies of less than 0-5 ms. The lowest thresholds for their generation were 0-15-0-20 muA in the spinal border cells and 0-35-0-40 muA in the motoneurones. In the main series on motoneurones a correlation has been established between different positions of the extracellular stimulating electrode in relation to the cells and the thresholds for the direct excitation of these cells. The position of the electrode were defined on the basis of an analysis of the IS and SD components of the action potentials recorded extracellularly around the cell when evoked by current pulses applied through the intracellular electrode; both the amplitudes of these IS and SD components and their timing with the IS and SD spikes, which were simultaneously recorded with the intracellular electrode, were then taken into account. The lowest thresholds (less than 2 muA) for the direct activation of cells were found nearest the initial segment of the axon. Their values increased to about 5 mu A at near-soma positions and to greater than 10 muA at near-dendrites positions about 150 mum away. 3. Transsynaptically evoked action potentials which were clearly set up by the preceding e.p.s.p.s appeared with latencies greater than 0-7 ms. When single current pulses were used, the lowest thresholds for transsynaptic spike activation were usually greater than 5-10 muA but they considerably decreased with repetitive stimuli. These thresholds were higher than the thresholds for the direct activation of cells within the region of the initial segment, of the same order of magnitude near the soma, and lower when the stimulating electrode was nearer the dendrites than the soma and generally at all larger distances from the cells. 4. All the observations on direct excitation of cells by extracellular stimuli (generation of the IS spike before the SD spike, lowest thresholds near the region of the initial segment of the axon, similar rates of increase in these thresholds with distance as for fibres) lead to the conclusion that the effects of the extracellular stimuli are exerted primarily via spread of current to the initial segment of the axon and its depolarization. 5. Late extracellular negativities presumably related to dendritic activation were observed in a few cells. These negativities were synchronous with late components of the intracellulary recorded action potentials.

Identification of cells of origin of long fiber connections in the cat's spinal cord by means of the retrograde axonal horseradish peroxidase technique

The location of the cells of origin of the propriospinal and long ascending spinal fibers has been determined by injecting horseradish peroxidase (HRP) unilaterally into the white and gray matter of the cat's spinal cord at cervical, thoracic and lumbar levels. In all cases retrogradely labeled neurons were present in the intermediate zone throughout the spinal cord. Caudal to the injections labeled neurons were also present in the dorsal horn, the column of Clarke and the area of the spinal border cells.

The location of cells of origin of the fibers in the ventral and the lateral funiculus of the cat's lumbo-sacral cord

Propriospinal fibers in different portions of ventral and lateral funiculi of cat's lumbo-sacral cord are distributed preferentially to different motoneuronal cell groups 28. The present study tried to determine the cells of origin of these fibers by means of the retrograde degeneration technique. In kittens either the spinal cord was hemisected at or above L1 or parts of ventral and lateral funiculi were transected between L4 and S1. The distribution of chromatolytic cells indicates that ascending pathways are derived mainly from cells in lamina IV and in lamina VIII as well as from large elements in the lateral part of the intermediate zone from L3 to L6 (area of spinal border cells). The results further indicate that short propriospinal fibers are derived mainly from cells in the intermediate zone. The bulk of these fibers in the ventral funiculus and ventral part of the lateral funiculus are derived from the medial and central parts of ipsilateral lamina VII. However, some fibers in the medial part of the ventral funiculus are derived also from contralateral lamina VIII while the fibers in the dorsal part of the lateral funiculus are derived mainly from the lateral parts of ipsilateral laminae VII, VI and V.

Functional organization of connexions to the ventral spinocerebellar tract

1. The functional organization of synaptic connexions to the ventral spinocerebellar tract (VSCT) has been investigated with intracellular recording from 89 spinal border cells (SBCs). 2. EPSPs from primary afferents. Monosynaptic group I EPSPs were evoked in 62 SBCs, in 50 of them from Ia afferents. Ia EPSPs were from knee extensors in 34 cells and knee flexors in 14 cells. No monosynaptic EPSP was evoked by stimulation of peripheral nerves in 27 SBCs. Dorsal column stimulation was tested in 15 of these cells; the absence of monosynaptic EPSPs in 14 of them proves the existence of VSCT cells without monosynaptic connexions from group I afferents. Polysynaptic EPSPs were woked in some cells from Ib afferents, high threshold muscle and cutaneous afferents. 3. IPSPs from primary afferents. Disynaptic IPSPs were evoked from Ia or Ib afferents in many cells. Ib IPSPs were common in SBCs without monosynaptic group I EPSPs. SBCs with Ia EPSPs received Ia or Ib IPSPs mainly from knee muscles. Convergence of Ia EPSPs and IPSPs from the same nerve was observed in 10 cells. Polysynaptic IPSPs were commonly evoked from Ib afferents and invariably evoked from high threshold muscle and skin afferents. 4. Stimulation of the ipsilateral dorsal and/or ventral quadrant of the spinal cord evoked monosynaptic EPSPs and/or IPSPs in many SBCs. 5. The results show that the synaptic input to the VSCT is much more complex than hitherto believed. It is pointed out that all investigated afferent systems, peripheral or descending, which evoke excitation also give inhibition.

Spinal border cell origin of the ventral spinocerebellar tract.

1. Extra- and intracellular recording has been made in cats from the spinal border cells (SBCs) of Cooper and Sherrington (1940). The SBCs were identified by their location in the lateral part of the ventral horn in the lumbar segments 3–6 and by their antidromic invasion from the contralateral thoracic spinal cord. 2. The conduction velocity of SBC axons ranged from 40–140 m/sec with a mean of 85 m/sec. 3. Lesion experiments showed that the SBC axons ascend in the ventrolateral region of the spinal cord. 4. Of 90 SBCs tested, 85 were invaded antidromically by stimulation of the cerebellar cortex. 5. It is concluded that SBCs give rise to ventral spinocerebellar axons and suggested that they are the major source of this tract.

D 13: Depression of Ia IPSP in Spinal Border Cells by Impulses in Recurrent Motor Axon Collaterals

D 13: Depression of Ia IPSP in Spinal Border Cells by Impulses in Recurrent Motor Axon Collaterals

The axonal pathways of spinal neurons in the cat.

AbstractThe axonal pathways of spinal neurons were studied in the cat using Ramón y Cajal's silver method.The cells of the ventral group of the nucleus supraspinalis contribute to the ventral roots of C1 and the cells of the dorsal group send their axons to the contralateral ventral funiculus. The cells of lamina VII send their axons to the ipsilateral lateral or ventrolateral funiculus. The subnucleus ventralis of the nucleus medullae oblongatae centralis sends axons to the lateral funiculus or to the ventral roots of C1. The cells of lamina V send their axons to the lateral funiculus and the contralateral ventral funiculus. The cells of lamina VII send their axons to the ipsilateral lateral funiculus and to the contralateral ventral funiculus. Numbers of spinal border cells were were observed in lamina IX at the level of the cervical and lumbar enlargement. It was found that the cell groups which were classified cytoarchitectonically contained numbers of different types of cells as judged by their axonal pathways.

Gower's Tract and “Spinal Border Cells”

Gower's Tract and “Spinal Border Cells”

GOWER'S TRACT AND SPINAL BORDER CELLS

Journal Article GOWER'S TRACT AND SPINAL BORDER CELLS Get access SYBIL COOPER, SYBIL COOPER Search for other works by this author on: Oxford Academic PubMed Google Scholar C. S. SHERRINGTON C. S. SHERRINGTON Search for other works by this author on: Oxford Academic PubMed Google Scholar Brain, Volume 63, Issue 2, June 1940, Pages 123–134, https://doi.org/10.1093/brain/63.2.123 Published: 01 June 1940