scholarly journals ON THE EXISTENCE OF A GRADIENT OF SENSITIVITY TO THE LACK OF SODIUM IN THE SPINAL ROOTS OF THE BULLFROG

1951 ◽  
Vol 35 (2) ◽  
pp. 183-201 ◽  
Author(s):  
R. Lorente de Nó
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Nerve Fibers ◽  
Nerve Trunk ◽  
Ventral Root ◽  
Gradual Change ◽  
Anatomical Distribution ◽  
Working Hypothesis ◽  
Temporal Course ◽  
Spinal Roots

The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers.

scholarly journals Radicular Myelinopathy in Aging Rats

1981 ◽  
Vol 18 (3) ◽  
pp. 335-341 ◽  
Author(s):  
G. Krinke ◽  
J. Suter ◽  
R. Hess
Keyword(s):  
Spinal Cord ◽  
Peripheral Nerves ◽  
Nerve Fibers ◽  
Male Rats ◽  
Aging Rats ◽  
Myelin Sheaths ◽  
Naturally Occurring ◽  
Spinal Roots

Naturally occurring degenerative lesions of nerve fibers in the spinal cord, spinal roots and peripheral nerves in nine male rats 877 days old were swollen myelin sheaths, forming “myelin bubbles.” The myelin swellings were distributed throughout the spinal tracts and the peripheral nerves, but most frequently in the lumbar ventral spinal roots. Although most axons surrounded by swollen myelin were intact, some were constricted and degenerated, while others showed signs of remyelination.

Effects of GABA, THIP, and potassium on excitability of myelinated axons of isolated amphibian spinal roots

1989 ◽  
Vol 67 (6) ◽  
pp. 682-685 ◽  
Author(s):  
S. Liske ◽  
M. E. Morris
Keyword(s):  
Action Potentials ◽  
Dorsal Root ◽  
Ventral Root ◽  
Aminobutyric Acid ◽  
Nerve Bundle ◽  
Myelinated Axons ◽  
Root Sheath ◽  
Compound Action Potentials ◽  
Spinal Roots ◽  
Compound Action

The effects of direct applications of GABA (γ-aminobutyric acid) and the GABAA agonist, THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) on the excitability of myelinated axons of individual dorsal and ventral spinal roots (lumbar VI and (or) VII) of the isolated bullfrog peripheral nerve are reported. Increases evoked by the GABA agonists (0.01–10 mM) in the amplitude of half-maximal A-fiber compound action potentials indicate the presence of depolarizing responses with apparently greater localization to the dorsal roots, and a sensitivity to GABA twofold greater than that for THIP. The changes evoked by GABA and THIP, as well as potassium have components that closely resemble those of sensory and motor fibers in the more distal, desheathed nerve bundle but are smaller and delayed, differences attributable to a closely attached root sheath that acts as a diffusion barrier. These results confirm the likely existence of GABAA receptors on both dorsal and ventral spinal roots.Key words: GABAA receptors, dorsal root fibers, ventral root fibers, depolarization, hyperpolarization.

Functional differences between afferent fibers in the hypogastric and pelvic nerves innervating female reproductive organs in the rat

1993 ◽  
Vol 69 (2) ◽  
pp. 533-544 ◽  
Author(s):  
K. J. Berkley ◽  
A. Robbins ◽  
Y. Sato
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Reproductive Tract ◽  
Nerve Fibers ◽  
Pelvic Nerve ◽  
Hypogastric Nerve ◽  
Afferent Fibers ◽  
Pelvic Nerves ◽  
Different Parts ◽  
Stimulation Of

1. The uterus, cervix, and vaginal canal are innervated by afferent fibers in the hypogastric and pelvic nerves. Four studies compared the innervation territory and sensitivity to peripheral stimuli of the two sets of fibers in adult virgin rats. 2. Innervation territory was studied anatomically by injecting different fluorescent dyes into different parts of the reproductive, lower urinary, and lower digestive tracts and examining retrogradely labeled neurons in dorsal root ganglia. It was also studied electrophysiologically in anesthetized rats by summing potentials evoked in branches of the two nerves by electrical stimulation of different parts of the reproductive tract. 3. In both studies sensory innervation of the reproductive tract shifted from the pelvic to the hypogastric nerve (i.e., shifted entry into the spinal cord from the L6-S1 to the T13-L3 dorsal root ganglia, respectively) as the dye or stimulating electrode shifted from the vaginal entrance to the uterine horns, with fibers from both nerves densely innervating the cervix region (i.e., entering the spinal cord through both sets of ganglia). The anatomic results suggested that the regions innervated by fibers in one nerve might also be innervated by a small component of normally quiescent fibers in the other nerve. 4. Response sensitivity was studied electrophysiologically by simultaneously recording multiunit activity in branches of the hypogastric and pelvic nerves in two ways. First, in intact, anesthetized rats, activity was recorded during mechanical stimulation of the reproductive tract (distension of the vagina and uterus, probing the cervix). Second, in an in vitro organ preparation of the uterus and vagina, activity was recorded during chemical stimulation through the uterine artery with bradykinin, serotonin, NaCN, CO2, and KCl. 5. Pelvic nerve fibers were markedly more sensitive than hypogastric nerve fibers to uterine and cervical mechanostimulation. Similarly, pelvic nerve fibers were more likely to respond or responded more vigorously than hypogastric nerve fibers to all chemical stimuli (except KCl). 6. These results provide strong evidence that afferent fibers in the pelvic and hypogastric nerves of nulliparous adult rats subserve different functions in reproduction and sensation. Pelvic nerve fibers seem closely tied to sensory and behavioral processes associated with mating and conception, whereas hypogastric fibers seem closely tied to pregnancy and nociception, with fibers in both nerves serving functions during parturition.

Microtubule and Neurofilament Densities in Amphibian Spinal Root Nerve Fibers: Relationship to Axoplasmic Transport

1973 ◽  
Vol 51 (11) ◽  
pp. 798-806 ◽  
Author(s):  
Richard S. Smith
Keyword(s):  
Dorsal Root ◽  
Dark Field ◽  
Nerve Fibers ◽  
Axoplasmic Transport ◽  
Spinal Root ◽  
Myelinated Nerve ◽  
Dorsal Roots ◽  
Dark Field Microscopy ◽  
Spinal Roots ◽  
Ventral Roots

Dark-field microscopy of living myelinated nerve fibers from the spinal roots of Xenopus laevis revealed many spherical organelles moving in the axoplasm of fibers from the ventral roots and in fibers just distal to the dorsal root ganglion. Similar organelles were present but few were seen to move along fibers from the dorsal roots central to the ganglion. This observation prompted an ultrastructural study of microtubule and neurofilament densities in the myelinated fibers of the spinal roots. The density of microtubules was significantly less in fibers from the central part of the dorsal roots than in the rest of the spinal root system. Neurofilament densities were equivalent in all parts of the roots. Microtubules showed a significant association with mitochondria in the ventral roots and in the dorsal roots distal to the ganglion, but no significant association was obtained for the dorsal roots central to the ganglion. The meaning of these results in the axoplasmic transport of large organelles is discussed.

scholarly journals Neoplasms of Mesenchymal Origin in the Spinal Cord and Nerve Roots of Three Dogs

1976 ◽  
Vol 13 (1) ◽  
pp. 47-58 ◽  
Author(s):  
M. Vandevelde ◽  
R. J. Higgins ◽  
C. E. Greene
Keyword(s):  
Spinal Cord ◽  
Malignant Tumors ◽  
Spinal Nerve ◽  
Nerve Fibers ◽  
Intramedullary Tumor ◽  
Reticulum Cell ◽  
Spinal Nerve Roots ◽  
Nerve Roots ◽  
Clinicopathological Findings ◽  
Spinal Roots

Clinicopathological findings of three different neoplastic conditions involving the spinal cord and nerve roots in three dogs are described. One sarcomatous intramedullary tumor closely associated with the vasculature was classified as a reticulum cell sarcoma of the spinal cord. The second case had massive and widespread neoplastic proliferation of reticulohistiocytic cells around the perineurinal vessels of many spinal nerve roots. The process was classified as a primary neoplastic reticulosis of the spinal roots. Multiple highly malignant tumors, infiltrating the spinal cord were found in one thoracic and several lumbosacral spinal nerve roots in the third case. These were considered to be anaplastic neurofibrosarcomas because of high collagen content, intact nerve fibers, whorl formation, and the tendency to palisade in some areas.

scholarly journals Central vs. peripheral neuraxial sympathetic control of porcine ventricular electrophysiology

2016 ◽  
Vol 310 (5) ◽  
pp. R414-R421 ◽  
Author(s):  
Kentaro Yamakawa ◽  
Kimberly Howard-Quijano ◽  
Wei Zhou ◽  
Pradeep Rajendran ◽  
Daigo Yagishita ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Stellate Ganglion ◽  
Afferent Input ◽  
Ventral Root ◽  
Spinal Root ◽  
Sympathetic Control ◽  
Thoracic Spinal ◽  
Yorkshire Pigs ◽  
Heart Electrophysiology

Sympathoexcitation is associated with ventricular arrhythmogenesis. The aim of this study was to determine the role of thoracic dorsal root afferent neural inputs to the spinal cord in modulating ventricular sympathetic control of normal heart electrophysiology. We hypothesize that dorsal root afferent input tonically modulates basal and evoked efferent sympathetic control of the heart. A 56-electrode sock placed on the epicardial ventricle in anesthetized Yorkshire pigs ( n = 17) recorded electrophysiological function, as well as activation recovery interval (ARI) and dispersion in ARI, at baseline conditions and during stellate ganglion electrical stimulation. Measures were compared between intact states and sequential unilateral T1–T4 dorsal root transection (DRTx), ipsilateral ventral root transection (VRTx), and contralateral dorsal and ventral root transections (DVRTx). Left or right DRTx decreased global basal ARI [Lt.DRTx: 369 ± 12 to 319 ± 13 ms ( P < 0.01) and Rt.DRTx: 388 ± 19 to 356 ± 15 ms ( P < 0.01)]. Subsequent unilateral VRTx followed by contralateral DRx+VRTx induced no further change. In intact states, left and right stellate ganglion stimulation shortened ARIs (6 ± 2% vs. 17 ± 3%), while increasing dispersion (+139% vs. +88%). There was no difference in magnitude of ARI or dispersion change with stellate stimulation following spinal root transections. Interruption of thoracic spinal afferent signaling results in enhanced basal cardiac sympathoexcitability without diminishing the sympathetic response to stellate ganglion stimulation. This suggests spinal dorsal root transection releases spinal cord-mediated tonic inhibitory control of efferent sympathetic tone, while maintaining intrathoracic cardiocentric neural networks.

Organization of peripheral nerves and spinal roots of the Atlantic stingray, Dasyatis sabina

1978 ◽  
Vol 41 (1) ◽  
pp. 97-107 ◽  
Author(s):  
R. E. Coggeshall ◽  
R. B. Leonard ◽  
M. L. Applebaum ◽  
W. D. Willis
Keyword(s):  
Dorsal Root Ganglion ◽  
Peripheral Nerves ◽  
Dorsal Root ◽  
Ganglion Cells ◽  
Ventral Root ◽  
Dasyatis Sabina ◽  
Unmyelinated Axons ◽  
Spinal Roots ◽  
Ventral Roots ◽  
Dorsal Root Ganglion Cells

1. The sizes and numbers of axons in peripheral nerves and spinal roots were investigated in the stingray, Dasyatis sabina. 2. The axons of the dorsal and ventral roots do not mingle in peripheral nerves of this animal as they do in higher vertebrates. Thus, it was usually possible to split the peripheral nerve into two portions, one containing only dorsal root axons, the other containing only ventral root axons. This feature was useful for the analysis of certain aspects of spinal cord organization. 3. The fact that dorsal and ventral root axons were segregated in peripheral nerves enabled us to demonstrate, without experimental surgery, that the central processes of the dorsal root ganglion cells and the proximal ventral root axons were 10-20% narrower, on the average, than the distal processes of the same dorsal root ganglion cells or the distal parts of the same ventral root axons. 4. The stingray is remarkable in having very few unmyelinated axons in the dorsal roots, ventral roots, or peripheral nerves. This paucity of unmyelinated axons distinguishes the Atlantic stingrays from all other vertebrates whose roots and nerves have been examined for unmyelinated fibers. 5. Similar findings were obtained for one spotted eagle ray (Aetobatus narinari) and two cow-nose rays (Rhinoptera bonasus).

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