Postsynaptic dorsal column pathway of the rat. I. Anatomical studies

1984 ◽  
Vol 51 (2) ◽  
pp. 260-275 ◽  
Author(s):  
G. J. Giesler ◽  
R. L. Nahin ◽  
A. M. Madsen
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Gray Matter ◽  
Dorsal Column ◽  
Spinal Cord Dorsal Horn ◽  
Substantia Gelatinosa ◽  
Cervical Cord ◽  
Dorsal Column Nuclei ◽  
Dorsal Columns ◽  
Postsynaptic Dorsal Column

As one of a series of studies of the ascending spinal cord pathways that might be involved in nociception in the rat, we have examined the projection to the dorsal column nuclei that originates in the spinal cord dorsal horn using the retrograde transport of horseradish peroxidase (HRP). This projection in other animals has been called the postsynaptic dorsal column (PSDC) pathway. Small iontophoretic injections of HRP into the cuneate nucleus (CN) labeled more than 350 neurons in alternate sections within the ipsilateral gray matter of segments C6-8. Fewer than 25 neurons were labeled in L4-6 by injections into CN. Injections of HRP confined to the gracile nucleus (GN) labeled more than 200 neurons within a narrow band extending across the ipsilateral dorsal horn subjacent to substantia gelatinosa of L4-6. Fewer than 10 cells were labeled in C6-8 by such injections. Labeling in lumbar neurons following injections into GN was prevented by transection of the dorsal columns at T10, T8, or C2. Thus, neurons labeled by such injections ascend entirely within the dorsal columns. Lesions of the dorsal columns in C2 reduced the number of labeled neurons in the cervical cord following CN injections by approximately 90%. Combined lesions of the dorsal columns and ipsilateral dorsal lateral funiculus (DLF) reduced the number of cells labeled in C6-8 by approximately 98%. Thus, the majority of labeled neurons in the cervical enlargement project to CN via the dorsal columns; a small secondary component of the cervical projection to CN appears to ascend within the DLF. To compare the relative sizes of the projections to the dorsal column nuclei from PSDC neurons and dorsal root ganglion cells (DRG), labeled neurons were counted in the gray matter of the cervical and lumbar enlargements and the corresponding DRG. In the four animals so examined, PSDC neurons constituted over 38% of the neurons that projected to CN and approximately 30% of the cells that projected to GN. These findings indicate that the PSDC projection of the rat is capable of providing a large somatotopically organized input to the dorsal column nuclei.

scholarly journals Sensory axons are guided by local cues in the developing dorsal spinal cord

Development ◽  
1998 ◽  
Vol 125 (4) ◽  
pp. 635-643 ◽  
Author(s):  
K. Sharma ◽  
E. Frank
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Gray Matter ◽  
Dorsal Spinal Cord ◽  
Sensory Axons ◽  
Ventral Cord ◽  
Dorsal Columns ◽  
Ia Projections ◽  
Dorsal Spinal ◽  
Local Cues

During development, different classes of sensory neurons establish distinctive central projections within the spinal cord. Muscle spindle afferents (Ia fibers) grow ventrally through the dorsal horn to the ventral cord, whereas cutaneous sensory collaterals remain confined to the dorsal horn. We have studied the nature of the cues used by Ia fibers in establishing their characteristic projections within the dorsal horn. An organotypic culture preparation of embryonic chicken spinal cord and sensory ganglia was used to test the influence of ventral spinal cord and local cues within the dorsal spinal cord on the growing Ia afferents. When the ventral half of the spinal cord was replaced with an inverted duplicate dorsal half, Ia fibers entering through the dorsal columns still grew ventrally within the host dorsal horn. After the fibers entered the duplicate dorsal half, they continued growing in the same direction. With respect to the duplicate dorsal tissue, this was in an opposite, ventral-to-dorsal, direction. In both cases, however, Ia collaterals remained confined to the medial dorsal laminae. Restriction to these laminae was maintained even when the fibers had to change their direction of growth to stay within them. These results show that cues from the ventral cord are not required for the development of correct Ia projections within the dorsal horn. Local, rather than long-range directional, cues appear to determine the pattern of these projections. When the ventral half of the spinal cord was left intact but sensory axons were forced to enter the dorsal gray matter growing rostrally or caudally, their collateral axons grew in random directions, further showing the absence of directional cues even when the ventral cord was present. Taken together, these observations suggest that Ia fibers are guided by local positional cues that keep them confined to the medial gray matter within the dorsal horn, but their direction of growth is determined primarily by their orientation and position as they enter the dorsal gray matter.

Norepinephrine Facilitates Inhibitory Transmission in Substantia Gelatinosa of Adult Rat Spinal Cord (Part 2)

2000 ◽  
Vol 92 (2) ◽  
pp. 485-485 ◽  
Author(s):  
Hiroshi Baba ◽  
Peter A. Goldstein ◽  
Manabu Okamoto ◽  
Tatsuro Kohno ◽  
Toyofumi Ataka ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Patch Clamp ◽  
Dorsal Horn ◽  
Dynamic Range ◽  
Spinal Cord Dorsal Horn ◽  
Substantia Gelatinosa ◽  
Inhibitory Interneurons ◽  
Patch Clamp Technique ◽  
Inhibitory Postsynaptic Currents ◽  
Postsynaptic Currents

Background It has been reported previously that norepinephrine, when applied to the spinal cord dorsal horn, excites a subpopulation of dorsal horn neurons, presumably inhibitory interneurons. In the current study, the authors tested whether norepinephrine could activate inhibitory interneurons, specifically those that are "GABAergic." Methods A transverse slice was obtained from a segment of the lumbar spinal cord isolated from adult male Sprague-Dawley rats. Whole-cell patch-clamp recordings were made from substantia gelatinosa neurons using the blind patch-clamp technique. The effects of norepinephrine on spontaneous GABAergic inhibitory postsynaptic currents were studied. Results In the majority of substantia gelatinosa neurons tested, norepinephrine (10-60 microM) significantly increased both the frequency and the amplitude of GABAergic inhibitory postsynaptic currents. These increases were blocked by tetrodotoxin (1 microM). The effects of norepinephrine were mimicked by the alpha1-receptor agonist phenylephrine (10-80 microM) and inhibited by the alpha1-receptor-antagonist WB-4101 (0.5 microM). Primary-afferent-evoked polysynaptic excitatory postsynaptic potentials or excitatory postsynaptic currents in wide-dynamic-range neurons of the deep dorsal horn were also attenuated by phenylephrine (40 microM). Conclusion The observations suggest that GABAergic interneurons possess somatodendritic alpha1 receptors, and activation of these receptors excites inhibitory interneurons. The alpha1 actions reported herein may contribute to the analgesic action of intrathecally administered phenylephrine.

Control of Size and Excitability of Mechanosensory Receptive Fields in Dorsal Column Nuclei by Homolateral Dorsal Horn Neurons

1998 ◽  
Vol 80 (1) ◽  
pp. 120-129 ◽  
Author(s):  
Robert W. Dykes ◽  
A. D. Craig
Keyword(s):  
Spinal Cord ◽  
Receptive Field ◽  
Dorsal Horn ◽  
Cobalt Chloride ◽  
Receptive Fields ◽  
Dorsal Column ◽  
Field Size ◽  
Dorsal Column Nuclei ◽  
Receptive Field Size ◽  
Dorsal Horn Neurons

Dykes, Robert W. and A. D. Craig. Control of size and excitability of mechanosensory receptive fields in dorsal column nuclei by homolateral dorsal horn neurons. J. Neurophysiol. 80: 120–129 1998. Both accidental and experimental lesions of the spinal cord suggest that neuronal processes occurring in the spinal cord modify the relay of information through the dorsal column-lemniscal pathway. How such interactions might occur has not been adequately explained. To address this issue, the receptive fields of mechanosensory neurons of the dorsal column nuclei were studied before and after manipulation of the spinal dorsal horn. After either a cervical or lumbar laminectomy and exposure of the dorsal column nuclei in anesthetized cats, the representation of the hindlimb or of the forelimb was defined by multiunit recordings in both the dorsal column nuclei and in the ipsilateral spinal cord. Next, a single cell was isolated in the dorsal column nuclei, and its receptive field carefully defined. Each cell could be activated by light mechanical stimuli from a well-defined cutaneous receptive field. Generally the adequate stimulus was movement of a few hairs or rapid skin indentation. Subsequently a pipette containing either lidocaine or cobalt chloride was lowered into the ipsilateral dorsal horn at the site in the somatosensory representation in the spinal cord corresponding to the receptive field of the neuron isolated in the dorsal column nuclei. Injection of several hundred nanoliters of either lidocaine or cobalt chloride into the dorsal horn produced an enlargement of the receptive field of the neuron being studied in the dorsal column nuclei. The experiment was repeated 16 times, and receptive field enlargements of 147–563% were observed in 15 cases. These data suggest that the dorsal horn exerts a tonic inhibitory control on the mechanosensory signals relayed through the dorsal column-lemniscal pathway. Because published data from other laboratories have shown that receptive field size is controlled by signals arising from the skin, we infer that the control of neuronal excitability, receptive field size and location for lemniscal neurons is determined by tonic afferent activity that is relayed through a synapse in the dorsal horn. This influence of dorsal horn neurons on the relay of mechanosensory information through the lemniscal pathways must modify our traditional views concerning the relative independence of these two systems.

Intravenous Opioids Stimulate Norepinephrine and Acetylcholine Release in Spinal Cord Dorsal Horn

1996 ◽  
Vol 84 (1) ◽  
pp. 143-154 ◽  
Author(s):  
Herve Bouaziz ◽  
Chuanyao Tong ◽  
Young Yoon ◽  
David D. Hood ◽  
James C. Eisenach
Keyword(s):  
Spinal Cord ◽  
Cerebrospinal Fluid ◽  
Dorsal Horn ◽  
Acetylcholine Release ◽  
Ventral Horn ◽  
Spinal Cord Dorsal Horn ◽  
Cervical Cord ◽  
Neural Pathways ◽  
Functional Studies ◽  
Intravenous Morphine

Background Opioids produce analgesia by direct effects as well as by activating neural pathways that release nonopioid transmitters. This study tested whether systematically administered opioids activate descending spinal noradrenergic and cholinergic pathways. Methods The effect of intravenous morphine on cerebrospinal fluid and dorsal horn microdialysate concentrations of norepinephrine and acetylcholine was examined in 20 sheep. Animals received either intravenous morphine or fentanyl alone, or morphine plus intravenous naloxone or intrathecal idazoxan. Results Intravenous morphine (0, 0.5, 1 mg/kg, intravenous) produced dose-dependent increases in cerebrospinal fluid norepinephrine and acetylcholine, but not epinephrine or dopamine. Morphine's effect was blocked by intravenous naloxone and by intrathecal idazoxan. In microdialysis experiments, intravenous morphine increased the concentration of norepinephrine and acetylcholine, but not epinephrine or dopamine, in the dorsal horn. In contrast, intravenous morphine exerted no effect on any of these monoamines in the ventral horn. Intravenous naloxone and cervical cord transection each blocked morphine's effect on dorsal horn norepinephrine. Conclusions These results support functional studies that indicate that systematically administered opioids cause spinal norepinephrine and acetylcholine release by a naloxone-sensitive mechanism. Idazoxan blockade of morphine's effects on cerebrospinal fluid norepinephrine was unexpected, and suggests that both norepinephrine and acetylcholine release in the spinal cord may be regulated by alpha 2-adrenoceptors. Microdialysis experiments suggest increased norepinephrine and acetylcholine levels in cerebrospinal fluid resulted from intravenous morphine-induced activation of bulbospinal pathways.

Effect of dorsal-column stimulation on gelatinosa and marginal neurons of cat spinal cord

1989 ◽  
Vol 70 (2) ◽  
pp. 257-265 ◽  
Author(s):  
David Dubuisson
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Synaptic Input ◽  
Time Course ◽  
Dorsal Column ◽  
Substantia Gelatinosa ◽  
Spinothalamic Tract ◽  
Nociceptive Responses ◽  
Excitatory Synaptic Input ◽  
Dorsal Column Stimulation

✓ Single neuronal units with physiological characteristics of superficial dorsal-horn neurons were recorded extracellularly in laminae 1, 2, and 3 of cat spinal cord. When focal electrical stimulation was applied to the ipsilateral dorsal column, most of the units were excited transsynaptically at various latencies consistent with an effect mediated by large myelinated axons. Units recorded in laminae 2 and 3 had earlier latencies of activation than units in lamina 1. Units with cutaneous receptive fields only for noxious stimuli were activated at significantly longer latencies than units responsive to innocuous stimuli. The time course of these effects was consistent with the concept that many cells in laminae 1 to 3 receive direct excitatory synaptic input from collaterals of dorsal-column fibers, and some lamina 1 cells receive excitatory synaptic input from lamina 2 neurons. Previous reports have emphasized the inhibitory action of dorsal-column stimulation on nociceptive responses of cells in laminae 4 and 5 of the dorsal-horn, particularly those of the spinocervical tract in cats and the spinothalamic tract in primates. The present study suggests that some of this inhibition might be sustained by a network of interneurons in or near the substantia gelatinosa and marginal layer. The therapeutic efficiency of dorsal-column stimulation for pain relief in humans may depend in part on the activation of neurons in the superficial layers of the dorsal horn.

scholarly journals Delta Opioid Receptors Presynaptically Regulate Cutaneous Mechanosensory Neuron Input to the Spinal Cord Dorsal Horn

Neuron ◽  
2014 ◽  
Vol 81 (6) ◽  
pp. 1443 ◽  
Author(s):  
Rita Bardoni ◽  
Vivianne L. Tawfik ◽  
Dong Wang ◽  
Amaury François ◽  
Carlos Solorzano ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Opioid Receptors ◽  
Spinal Cord Dorsal Horn ◽  
Mechanosensory Neuron ◽  
Delta Opioid Receptors ◽  
Spinal Cord Dorsal
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