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Coggeshall RE, Kandel ER, Kupfermann I, Waziri R. A morphological and functional study on a cluster of identifiable neurosecretory cells in the abdominal ganglion of aplysia californica. ACTA ACUST UNITED AC 2010; 31:363-8. [PMID: 19866706 PMCID: PMC2107051 DOI: 10.1083/jcb.31.2.363] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R E Coggeshall
- Department of Anatomy, Harvard Medical School, Boston, and the Departments of Physiology and Psychiatry, New York University School of Medicine, New York
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Gao J, Coggeshall RE, Tarasenko YI, Wu P. Human neural stem cell-derived cholinergic neurons innervate muscle in motoneuron deficient adult rats. Neuroscience 2005; 131:257-62. [PMID: 15708470 DOI: 10.1016/j.neuroscience.2004.10.033] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2004] [Indexed: 12/23/2022]
Abstract
Motoneuron damage occurs in spinal cord injury and amyotrophic lateral sclerosis. Current advances offer hope that human embryonic stem cells [Science 282 (1998) 1145] or neural stem cells (NSC) [Exp Neurol 161 (2000) 67; Exp Neurol 158 (1999) 265; J Neurosci Methods 85 (1998) 141; Proc Natl Acad Sci USA 97 (2000) 14720; Exp Neurol 156 (1999) 156 ] may be donors to replace lost motoneurons. Previously, we developed a priming procedure that produced cholinergic cells that resemble motoneurons from human NSCs grafted into adult rat spinal cord [Nat Neurosci 5 (2002a) 1271]. However, effective replacement therapy will ultimately rely on successful connection of new motoneurons with their muscle targets. In this study, we examined the potential of human fetal NSC transplantation to replace lost motoneurons in an animal model of chronic motoneuron deficiency (newborn sciatic axotomy) [J Comp Neurol 224 (1984) 252; J Neurobiol 23 (1992) 1231]. We found, for the first time, that human neural stem cell-derived motoneurons send axons that pass through ventral root and sciatic nerve to form neuromuscular junctions with their peripheral muscle targets. Furthermore, this new cholinergic innervation correlates with partial improvement of motor function.
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Affiliation(s)
- J Gao
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1043, USA
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3
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Abstract
Our hypothesis is that peripheral somatostatin (SRIF) has a role in counter-irritation-induced analgesia. Our paradigm involves the reduction of nociceptive behaviors produced by primary noxious stimuli (formalin or complete Freund's adjuvant [CFA] in the rat hind paw) by a counter-irritating stimulus (capsaicin [CAP] in the tail or muzzle). Activation of peripheral SRIF receptors is key since an SRIF receptor antagonist cyclo-somatostatin (c-SOM) and SRIF antibodies in the hind paw attenuate the counter-irritation-induced analgesia of both formalin and more persistent CFA nociception. Specificity of c-SOM is shown by reversal of its effects with octreotide, a SRIF analog. Injection of formalin in one hind paw and c-SOM in the other does not reduce the counter-irritation analgesia demonstrating local action of the c-SOM. Approximately 33% of peripheral sensory axons contain SRIF, which could release the peptide to activate SRIF receptors on cutaneous axons. Intraplantar naloxone has no effect on the counter-irritation analgesia indicating that SRIF is not activating opioid receptors. These results indicate that in addition to the classic central descending noxious inhibitory control systems that underlie counter-irritation-induced analgesia, there is a peripheral contribution arising from activation of SRIF receptors. Identifying a peripheral contribution of SRIF to mechanisms of counter-irritation analgesia offers opportunities for peripheral therapy.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, 301 University Boulevard, University of Texas Medical Branch, Galveston, TX 77555-1069, USA.
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Abstract
The present study investigates the contribution of peripheral N-methyl-D-aspartate (NMDA) receptors to acute nociception and persistent inflammatory pain in the rat. Immunohistochemical localization of the NMDA receptor one (NMDAR1) subunit demonstrates that 47% of unmyelinated axons in the normal digital nerve are positively labeled. In concert with the overall progression of inflammation following injection of complete Freund's adjuvant (CFA) in the hind paw, a significant increase in the proportion of NMDAR1-labeled unmyelinated digital axons occurs at 2 and 7, but not 14 days following hind-paw inflammation. In behavioral studies, we confirm an increased mechanical sensitivity in CFA-injected hind paws. Furthermore, activation of NMDA receptors following intraplantar NMDA (1.0 mM) in normal animals results in a mechanical sensitivity similar to that observed in inflamed animals. Conversely, a low concentration of NMDA (0.5 mM) that has little affect on mechanical thresholds in normal animals produces a significant increase in mechanical sensitivity in the inflamed state. CFA-induced mechanical sensitivity involves NMDA-receptor activation demonstrated by the observation that injection of MK-801 alone into the inflamed hind paw returns mechanical sensitivity to normal (pre-inflammation) levels. In single-unit studies, there is a dose-dependent increase in NMDA-induced nociceptor activity in both normal and inflamed skin, but the amount of NMDA required to induce activation is reduced in inflamed skin. In addition, NMDA-induced discharge rates and percentage of NMDA-activated nociceptors are significantly increased in inflamed compared with normal skin, and this activation can be blocked by co-administration of MK-801. Exposure of nociceptors in normal skin to 1 mM NMDA sensitizes the units to reapplication of NMDA and to heat. Nociceptors that demonstrate sensitization to heat in persistent inflammation show an enhanced sensitization when exposed to exogenous NMDA. Thus, peripheral NMDA receptors not only play an important role in modulating the responses of nociceptors in normal skin, but their upregulation and activation on peripheral nociceptors contributes significantly to the mechanical sensitivity and heat sensitization that accompanies persistent inflammation.
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Affiliation(s)
- J Du
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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5
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Abstract
The goal of the present study is to determine the relationship of metabotropic glutamate receptors 2/3 (mGluR2/3) to dorsal root ganglion cells, peripheral primary afferent fibers in digital nerves and central primary afferent fibers in the spinal cord. We demonstrate that approximately 40% of L4 and L5 dorsal root ganglion cells contain mGluR2/3-like immunoreactivity. These mGluR2/3-positive cells are small in diameter (23 microm) and 76% stain for the isolectin Griffonia simplicifolia (I-B4), while 67% of I-B4 cells have mGluR2/3-like immunoreactivity. Electron microscopic analyses of mGluR2/3-like immunoreactivity in axons in digital nerves indicate that 32% of unmyelinated and 28% of myelinated axons are labeled. In the lumbar dorsal horn, mGluR2/3-like immunoreactivity is localized preferentially in lamina IIi with lighter staining in laminae III and IV. The dense mGluR2/3-like immunoreactivity in lamina IIi is consistent with the localization of these receptors in I-B4-labeled dorsal root ganglion cells. Elimination of primary afferent input following unilateral dorsal rhizotomies significantly decreases the mGluR2/3-like immunoreactivity density in the dorsal horn although some residual staining does remain, suggesting that many but not all of these receptors are located on primary afferent processes. The finding that mGluR2/3s are located on peripheral sensory axons suggests that they are involved in peripheral sensory transduction and can modulate transmission of sensory input before it reaches the spinal cord. This offers the possibility of altering sensory input, particularly noxious input, at a site that would avoid CNS side effects. Since many but not all of these receptors are located on primary afferent terminals, these receptors may also influence primary afferent transmission in the dorsal horn through presynaptic mechanisms and glutamatergic transmission in general through both presynaptic and postsynaptic mechanisms. Since these receptors are concentrated in lamina IIi and also largely co-localized with I-B4, they may have considerable influence on nociceptive processing by what are considered to be non-peptidergic primary afferent neurons.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1069, USA.
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Abstract
The vanilloid receptor-1 (VR1) is activated by capsaicin, heat and protons and is localized on primary sensory neurons. The present study investigates whether VR1 increases in the inflamed hindpaw thereby contributing to the peripheral sensitization and heat hyperalgesia that characterizes the inflamed state. Forty-eight hours after intraplantar injection of Complete Freund's Adjuvant into one hindpaw, there is a significant increase in the proportion of VR1-labeled unmyelinated axons in digital nerves in the inflamed (32.8 +/- 5.9%) compared to normal (17.1 +/- 2.6%) hindpaws (t-test, P<0.01). A few, small diameter myelinated axons are labeled in normal and inflamed rats with no change in percentages following inflammation. The data suggest that an increase in number of unmyelinated sensory axons expressing VR1 may be one mechanism underlying peripheral sensitization of nociceptors in inflammation.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555-1069, USA.
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7
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Coggeshall RE, Lekan HA, White FA, Woolf CJ. A-fiber sensory input induces neuronal cell death in the dorsal horn of the adult rat spinal cord. J Comp Neurol 2001; 435:276-82. [PMID: 11406811 DOI: 10.1002/cne.1029] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Excitotoxicity due to excessive synaptic glutamate release is featured in many neurological conditions in which neuronal death occurs. Whether activation of primary sensory pathways can ever produce sufficient over-activity in secondary sensory neurons in the dorsal horn of the spinal cord to induce cell death, however, has not been determined. In this study, we asked whether activity in myelinated afferents (A fibers), which use glutamate as a transmitter, can induce cell death in the dorsal horn. Using stereological estimates of neuron numbers from electron microscopic sections, we found that stimulation of A-fibers in an intact sciatic nerve at 10 Hz, 20 Hz, and 50 Hz in 10-minute intervals at a stimulus strength that activates both Abeta and Adelta fibers resulted in the loss of 25% of neurons in lamina III, the major site of termination of large Abeta fibers, but not in lamina I, where Adelta fibers terminate. Furthermore, sciatic nerve lesions did not result in detectable neuron loss, but activation of A fibers in a previously sectioned sciatic nerve did cause substantial cell death not only in lamina III but also in laminae I and II. The expansion of the territory of A-fiber afferent-evoked cell death is likely to reflect the sprouting of the fibers into these laminae after peripheral nerve injury. The data show, therefore, that primary afferent A-fiber activity can cause neuronal cell death in the dorsal horn with an anatomical distribution that depends on whether intact or injured fibers are activated. Stimulation-induced cell death potentially may contribute to the development of persistent pain.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neuroscience, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA.
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9
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Carlton SM, Du J, Zhou S, Coggeshall RE. Tonic control of peripheral cutaneous nociceptors by somatostatin receptors. J Neurosci 2001; 21:4042-9. [PMID: 11356891 PMCID: PMC6762714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2023] Open
Abstract
The peptide somatostatin [somatotropin release-inhibiting factor (SRIF)] is widely distributed in the body and exerts a variety of hormonal and neural actions. Several lines of evidence indicate that SRIF is important in nociceptive processing: (1) it is localized in a subset of small-diameter dorsal root ganglion cells; (2) activation of SRIF receptors results in inhibition of both nociceptive behaviors in animals and acute and chronic pain in humans; (3) SRIF inhibits dorsal horn neuronal activity; and (4) SRIF reduces responses of joint mechanoreceptors to noxious rotation of the knee joint. The goal of the present study is to show that cutaneous nociceptors are under the tonic inhibitory control of SRIF. This is accomplished using behavioral and electrophysiological paradigms. In a dose-dependent manner, intraplantar injection of the SRIF receptor antagonist cyclo-somatostatin (c-SOM) results in nociceptive behaviors in normal animals and enhancement of nociceptive behaviors in formalin-injected animals, and these actions can be blocked when c-SOM is coapplied with three different SRIF agonists. Furthermore, intraplantar injection of SRIF antiserum also results in nociceptive behaviors. Electrophysiological recordings using an in vitro glabrous skin-nerve preparation show increased nociceptor activity in response to c-SOM, and this increase is blocked by the same three SRIF agonists. Parallel behavioral and electrophysiological studies using the opioid antagonist naloxone demonstrate that endogenous opioids do not maintain a tonic inhibitory control over peripheral nociceptors, nor does opioid receptor antagonism influence peripheral SRIF effects on nociceptors. These findings demonstrate that SRIF receptors maintain a tonic inhibitory control over peripheral nociceptors, and this may contribute to mechanisms that control the excitability of these terminals.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA.
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10
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Abstract
The present study deals with changes in numbers and sizes of primary afferent neurons (dorsal root ganglion [DRG] cells) after sciatic nerve transection. We find that this lesion in adult rats leads to death of some DRG cells by 8 weeks and 37% by 32 weeks after the lesion. The loss of cells appears earlier in and is more severe in B-cells (small, dark cells with unmyelinated axons) than A-cells (large, light cells with myelinated axons). With regard to mean cell volumes, there is a tendency for both categories of DRG cells to be smaller, but except for isolated time points, these differences are not statistically significant. These findings differ from most earlier reports in that the cell loss takes place later than usually reported, that the loss is more severe for B-cells, and that neither A- or B-cells change size significantly. Accordingly, we conclude that sciatic nerve transection in adult rats leads to a slowly developing but relatively profound loss of primary afferent neurons that is more severe for B-cells. These results can serve as a basis for studies to determine the effectiveness of trophic or survival factors in avoiding axotomy induced cell death.
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Affiliation(s)
- T Tandrup
- Department of Neurology, University Hospital of Aarhus and Stereological Research Laboratory, University of Aarhus, DK-8000C, Denmark.
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11
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Abstract
Sympathetic efferents are involved in the pain of inflammation. Thus the control of these fibers is a matter of considerable importance. In this regard, postganglionic sympathetic fibers in normal rats express ionotropic glutamate receptors. The present study tests the hypothesis that inflammation leads to a significant increase in numbers of sympathetic efferents that express these receptors. In normal rats, the percentage of fibers in the L4 and L5 sympathetic gray rami immunostained with antibodies against subunits of NMDA (NMDAR1), AMPA (GluR1), or kainate (GluR5,6,7) receptors are 29, 5 and 5%, respectively. Forty-eight hours following injection of complete Freund's adjuvant into one hindpaw, the percentages of fibers in the ipsilateral gray rami immunostained for NMDA, AMPA or kainate are 57, 52 and 48%, respectively. Thus, following inflammation there is a two-fold increase in axons expressing NMDA receptors and a ten-fold increase in axons expressing AMPA or kainate receptors. These data suggest that postganglionic activity may be enhanced by glutamate receptor activation during inflammation. Increased activity in postganglionic fibers could lead to an increased release of NE and other substances in postganglionic efferents such as prostaglandins which in turn could enhance nociceptor activity. This change in glutamate receptor organization offers a possible site of pharmacological intervention for the maladaptive symptoms that often arise following peripheral inflammation.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, 301 University Blvd., University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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12
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Lewis SE, Mannion RJ, White FA, Coggeshall RE, Beggs S, Costigan M, Martin JL, Dillmann WH, Woolf CJ. A role for HSP27 in sensory neuron survival. J Neurosci 1999; 19:8945-53. [PMID: 10516313 PMCID: PMC6782783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/1999] [Accepted: 08/06/1999] [Indexed: 02/14/2023] Open
Abstract
Peripheral nerve injury in neonatal rats results in the death of the majority of the axotomized sensory neurons by 7 d after injury. In adult animals, however, all sensory neurons survive for at least 4 months after axotomy. How sensory neurons acquire the capacity to survive axonal injury is not known. Here we describe how the expression of the small heat shock protein 27 (HSP27) is correlated with neuronal survival after axotomy in vivo and after NGF withdrawal in vitro. The number of HSP27-immunoreactive neurons in the L4 DRG is low at birth and does not change significantly for 21 d after postnatal day 0 (P0) sciatic nerve axotomy. In contrast, in the adult all axotomized neurons begin to express HSP27. One week after P0 sciatic nerve section the total number of neurons in the L4 DRG is dramatically reduced, but all surviving axotomized neurons, as identified by c-jun immunoreactivity, are immunoreactive for HSP27. In addition, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling reveals that very few HSP27-expressing neurons are dying 48 hr after neonatal axotomy. In vitro, a similar correlation exists between HSP27 expression and survival; in P0 DRG cultures, neurons that express HSP27 preferentially survive NGF withdrawal. Finally, overexpression of human HSP27 in neonatal rat sensory and sympathetic neurons significantly increases survival after NGF withdrawal, with nearly twice as many neurons surviving at 48 hr. Together these results suggest that HSP27 in sensory neurons plays a role in promoting survival after axotomy or neurotrophin withdrawal.
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Affiliation(s)
- S E Lewis
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129, USA
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13
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Abstract
We propose that the primary afferent depolarization that follows GABA(A) receptor activation in the spinal cord also occurs in the periphery. As evidence, the present study localizes beta2/beta3 and alpha1 subunits of the GABA(A) receptor on 10-14% of the unmyelinated primary afferents axons in the glabrous skin of the cat paw. Behavioral studies demonstrate that local peripheral injection of the GABA(A) agonist muscimol at a low concentration (2.0 microM) attenuates, and at a high concentration (1 mM) enhances, formalin-induced nociceptive behaviors. Intraplantar injection of muscimol alone at a high dose evokes thermal hyperalgesia. Bicuculline, a GABA(A) antagonist, prevents these muscimol-induced changes in behavior. The muscimol-induced effects are due to local rather than systemic or central activation of GABA(A) receptors, as such effects are not observed in the contralateral paw. We interpret these findings to indicate that activation of GABA(A) receptors by low concentrations of muscimol depolarizes peripheral primary afferent terminals, a phenomenon we call peripheral primary afferent depolarization, in turn reducing the size of the peripheral action potentials and concomitantly reducing the amount of algogenic substances released from the peripheral terminals of these fibers. This sequence of events presumably results in a reduction in nociceptor activation. Higher concentrations of muscimol further depolarize GABA(A) receptor-containing terminals, which then initiates action potentials in nociceptors analogous to the appearance of dorsal root reflexes that arise following activation of GABA(A) receptors on central primary afferent terminals. These latter events reverse the analgesic effects of GABA(A) ligands and lead to potentiation of nociceptive input. Thus, the present study provides anatomical and behavioral evidence supporting a bimodal role for GABA(A) receptors in the modulation of peripheral nociceptive transmission.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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14
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Abstract
Most of the biological effects of nerve growth factor (NGF) are mediated by TrkA, the high affinity receptor for NGF. Previous studies have shown that NGF levels in the dorsal root ganglia (DRG) fluctuate following a peripheral nerve injury. The present study examined changes of TrkA immunoreactivity and trkA mRNA expression in the DRG after segmental nerve ligation. In the normal L5 DRG of the rat, there were, on average, 4700 TrkA-immunoreactive (TrkA-IR) neurons, representing 42% of the total neuronal population. Following L5 spinal nerve ligation, the number of TrkA-IR neurons in the L5 DRG slowly declined, reducing by 25% at 1 week and 35% at 3 weeks postoperation (PO). In contrast, trkA mRNA in these ganglia showed a significant decrease from 3 days to 3 weeks PO and was followed by a full recovery at 2 months PO. The early decrease of trkA mRNA is likely due to deprivation of target-derived NGF, which is caused by nerve ligation, and the recovery might be because substitute sources of NGF become available. Despite the decline in trkA mRNA in the ganglion, 3000 injured DRG neurons sustain TrkA immunoreactivity, suggesting that exogenous NGF can still influence these TrkA expressing neurons, even though they are isolated from the periphery. Accordingly, the effects of endogenous NGF should be as well manifested by local administration of NGF to the ganglion as to the stump of the damaged nerve.
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Affiliation(s)
- H Shen
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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15
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Abstract
The ionotropic glutamate receptors N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate (KA) have been localized on subpopulations of unmyelinated and myelinated sensory axons in normal skin. Behavioral studies indicate that activation of these receptors results in nociceptive behaviors and contributes to inflammatory pain. The goal of the present study was to determine if these glutamate receptors might contribute to the peripheral hypersensitivity observed in inflammation. The major findings were that 48 h following complete Freund's adjuvant (CFA)-induced inflammation, the proportions of unmyelinated axons labeled for NMDA, AMPA or KA receptors were 61%, 43% and 48%, respectively, in cutaneous nerves in the inflamed paw compared to 48%, 22% and 27%, respectively, in the non-inflamed paw. The proportions of myelinated axons labeled for NMDA, AMPA or KA receptors were 61%, 61% and 43%, respectively, compared to 43%, 42% and 28%, respectively, in the non-inflamed hindpaw. These increases were all significant. These data indicate that the number of sensory axons containing ionotropic glutamate receptors increases during inflammation, and this may be a contributing factor to peripheral sensitization in inflammation.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1069, USA.
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Costigan M, Mannion RJ, Kendall G, Lewis SE, Campagna JA, Coggeshall RE, Meridith-Middleton J, Tate S, Woolf CJ. Heat shock protein 27: developmental regulation and expression after peripheral nerve injury. J Neurosci 1998; 18:5891-900. [PMID: 9671676 PMCID: PMC6793078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The heat shock protein (HSP) 27 is constitutively expressed at low levels in medium-sized lumbar dorsal root ganglion (DRG) cells in adult rats. Transection of the sciatic nerve results in a ninefold upregulation of HSP27 mRNA and protein in axotomized neurons in the ipsilateral DRG at 48 hr, without equivalent changes in the mRNAs encoding HSP56, HSP60, HSP70, and HSP90. Dorsal rhizotomy, injuring the central axon of the DRG neuron, does not upregulate HSP27 mRNA levels. After peripheral axotomy, HSP27 mRNA and protein are present in small, medium, and large DRG neurons, and HSP27 protein is transported anterogradely, accumulating in the dorsal horn and dorsal columns of the spinal cord, where it persists for several months. Axotomized motor neurons also upregulate HSP27. Only a minority of cultured adult DRG neurons are HSP27-immunoreactive soon after dissociation, but all express HSP27 after 24 hr in culture with prominent label throughout the neuron, including the growth cone. HSP27 differs from most axonal injury-regulated and growth-associated genes, which are typically present at high levels in early development and downregulated on innervation of their targets, in that its mRNA is first detectable in the DRG late in development and only approaches adult levels by postnatal day 21. In non-neuronal cells, HSP27 has been shown to be involved both in actin filament dynamics and in protection against necrotic and apoptotic cell death. Therefore, its upregulation after adult peripheral nerve injury may both promote survival of the injured neurons and contribute to alterations in the cytoskeleton associated with axonal growth.
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Affiliation(s)
- M Costigan
- Department of Anatomy and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
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17
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Abstract
It is known that Substance P (SP) enhances glutamate- and N-methyl-D-aspartate (NMDA)-induced activity in spinal cord dorsal horn neurons and that this enhancement is important in the generation of wind-up and central sensitization. It is now known that SP and glutamate receptors are present on sensory axons in rat glabrous skin. This raises the issue as to whether SP and glutamate interact in the periphery. Using the tail skin in rats, the present study demonstrates 1) that unmyelinated axons at the dermal-epidermal junction immunostain for antibodies directed against NMDA, non-NMDA or SP (NK1) receptors; 2) that glutamate injected into the tail skin results in dose-dependent nociceptive behaviors interpreted as mechanical hyperalgesia, mechanical allodynia and thermal hyperalgesia, which are blocked following co-injection with glutamate antagonists; 3) that peripheral injection of SP potentiates glutamate-induced nociceptive behaviors in that the co-injection of SP+glutamate results in a significantly longer duration of behavioral responses compared to the responses seen following injection of either substance alone. These data provide support for the hypothesis that primary afferent neurons might well be subject to similar mechanisms that result in wind-up or central sensitization of spinal cord neurons.
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MESH Headings
- 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology
- Animals
- Axons/chemistry
- Axons/ultrastructure
- Behavior, Animal/physiology
- Dizocilpine Maleate/pharmacology
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Antagonists/pharmacology
- Glutamic Acid/metabolism
- Glutamic Acid/pharmacology
- Hot Temperature
- Hyperalgesia/metabolism
- Male
- Microscopy, Immunoelectron
- Neurons, Afferent/chemistry
- Neurons, Afferent/drug effects
- Neurons, Afferent/ultrastructure
- Nociceptors/drug effects
- Nociceptors/physiology
- Pain/physiopathology
- Physical Stimulation
- Rats
- Rats, Sprague-Dawley
- Receptors, AMPA/analysis
- Receptors, AMPA/chemistry
- Receptors, AMPA/metabolism
- Receptors, N-Methyl-D-Aspartate/analysis
- Receptors, N-Methyl-D-Aspartate/chemistry
- Receptors, N-Methyl-D-Aspartate/metabolism
- Receptors, Neurokinin-1/metabolism
- Skin/innervation
- Skin/ultrastructure
- Substance P/pharmacology
- Tail
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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18
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Abstract
The present study demonstrates that approximately 36% of postganglionic sympathetic axons in gray rami express receptors for the N-methyl-D-aspartate receptor 1 subunit of the N-methyl-D-aspartate receptor and 10% express the glutamate receptor 1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. If these receptors are active, glutamate released from primary afferent terminals could activate these receptors resulting in the release of noradrenaline and other substances from postganglionic sympathetic neurons. This interaction would constitute a non-synaptic, sensory-sympathetic, peripheral reflex that might be important in local vascular control and in pain states that have a sympathetic component.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, University of Texas Medical Branch, Galveston 77555-1069, USA
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19
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Carlton SM, Hargett GL, Coggeshall RE. Plasticity in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunits in the rat dorsal horn following deafferentation. Neurosci Lett 1998; 242:21-4. [PMID: 9509995 DOI: 10.1016/s0304-3940(98)00036-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Immunostaining for GluR1 and GluR2/3 subunits of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor is prominent in laminae I and II of the normal dorsal horn, with much less staining in deeper laminae. Three days after dorsal rhizotomy, image analysis demonstrates a significant decrease in staining density for both antibodies in the superficial dorsal horn. By contrast, staining density is significantly increased in laminae III, IV and the reticulated region of lamina V for GluR1 only. This increase suggests that AMPA receptors contribute to deafferentation or radicular pain by at least two mechanisms: (1) up-regulation of GluR1 subunits of the AMPA receptor in deeper laminae, and (2) enhanced Ca2+ permeability of dorsal horn neurons because AMPA receptors lacking the GluR2 subunit are Ca2+ permeable. Glutamate activation of these receptors could initiate or potentiate second messenger cascades that could well contribute to neuronal changes documented in the dorsal horn of deafferented animals.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA.
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20
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Abstract
The present study determines the proportions of unmyelinated cutaneous axons at the dermal-epidermal junction in glabrous skin and of myelinated and unmyelinated axons in the sural and medial plantar nerves that immunostain for subunits of the ionotropic glutamate receptors. Approximately 20% of the unmyelinated cutaneous axon profiles at the dermal-epidermal junction immunostain for either N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), or kainate receptor subunits. These findings are consistent with previous observations that NMDA and non-NMDA antagonists ameliorate nociceptive behaviors that result from noxious peripheral stimulation. In the sural nerve, where the large majority of myelinated fibers are sensory, approximately half of the myelinated axon profiles immunostain for the NMDA receptor 1 (R1) subunit, 28% immunostain for the glutamate receptor 1 (GluR1) AMPA subunit, and 11% for the GluR5,6,7 kainate subunits. Even higher proportions immunostain for these receptors in the medial plantar nerve, a mixed sensory and motor nerve. In the sural nerve, 20% of the unmyelinated axon profiles immunostain for NMDAR1 and only 7% label for GluR1 or GluR5,6,7. Because the sural nerve innervates hairy skin, these data suggest that glutamate will activate a higher proportion of unmyelinated axons in glabrous skin than in hairy skin. Measurements of fiber diameters indicate that all sizes of myelinated axon profiles, including Adelta and Abeta, are positively labeled for the ionotropic receptors. The presence of glutamate receptors on large-diameter myelinated axons suggests that these mechanosensitive receptors, presumably transducing touch and pressure, may also respond to local glutamate and thus be chemosensitive.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA.
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21
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Lekan HA, Chung K, Yoon YW, Chung JM, Coggeshall RE. Loss of dorsal root ganglion cells concomitant with dorsal root axon sprouting following segmental nerve lesions. Neuroscience 1997; 81:527-34. [PMID: 9300439 DOI: 10.1016/s0306-4522(97)00173-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Tight ligation of the fifth and sixth lumbar segmental nerves in the rat provides a model of neuropathic pain. We used this model to assess the changes in primary afferent input to the dorsal horn in neuropathic pain syndromes. Dorsal roots and ganglia were examined for up to 32 weeks following segmental nerve ligation. Stereologic and morphometric techniques revealed a notable decrease in the numbers of dorsal root ganglion cells and unmyelinated dorsal root axons by six weeks post-injury. By 32 weeks following segmental nerve ligations, the numbers of dorsal root ganglion cells have dropped to 50% of pre-ligation levels while the numbers of dorsal root axons have increased to normal levels predominantly due to sprouting of myelinated fibres. These findings indicate that although there is a great loss of dorsal root ganglion cells, there is dramatic sprouting of myelinated fibres and possibly some sprouting of unmyelinated fibres in the dorsal roots. Additionally, a difference in the responses of unmyelinated and myelinated fibres to this peripheral nerve injury is revealed. These changes in dorsal root ganglion cells and their central axons may underlie certain aspects of abnormal pain syndromes because of changes in the types and quantity of input the dorsal horn receives.
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Affiliation(s)
- H A Lekan
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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22
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Abstract
The mu opioid receptor is concentrated in laminae I and II (LI and LII, respectively) of the normal rat dorsal horn. Fourteen days after transection of the L4-L6 segmental peripheral nerves, image analysis demonstrates a 49, 34 and 17% decrease in mu opioid staining density in the medial, middle and lateral thirds of the superficial dorsal horn, respectively, when comparing the operated to the unoperated side. Intralaminar analysis demonstrates that the greatest change in density occurs in LI and LII outer, compared to LII inner. By 31 days post-surgery, staining has returned to normal with side to side differences no longer present. These results imply that mu opioid ligands such as morphine might be less effective in ameliorating pain 2 weeks after a peripheral nerve lesion than they are in the normal condition, but that this effectiveness should return as the receptors are restored to their normal levels. Thus, the time following a lesion may be an important variable in assessing the effectiveness of mu opioid ligands in alleviating neuropathic pain. Furthermore, this study shows that the organization of opioid receptors in the superficial dorsal horn is malleable and could lead to changes in drug efficacy.
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Affiliation(s)
- J F deGroot
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, Galveston, TX 77555-1069, USA
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23
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Abstract
Opioid receptors have been demonstrated by light microscopic techniques in fine cutaneous nerves in naive animals. The present study extends these findings by showing that 29 and 38% of unmyelinated cutaneous sensory axons can be immunostained for mu- or delta-opioid receptors respectively. Local cutaneous injection of DAMGO, a mu-opioid ligand, ameliorates the nociceptive behaviors caused by local cutaneous injection of glutamate, a purely nociceptive chemical stimulus showing that the mu-receptors are functional. By contrast the delta-opioid ligand [2-D-penicillamine, 5-D-penicillamine]enkephalin (DPDPE) had no effect on these behaviors. These findings indicate a wider function for opioid receptors in naive animals than previously envisioned.
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MESH Headings
- Animals
- Axons/drug effects
- Axons/metabolism
- Axons/ultrastructure
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Dose-Response Relationship, Drug
- Glutamic Acid/pharmacology
- Immunohistochemistry
- Inflammation/pathology
- Male
- Narcotic Antagonists
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Neurons, Afferent/ultrastructure
- Peripheral Nervous System/cytology
- Peripheral Nervous System/drug effects
- Peripheral Nervous System/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid/agonists
- Receptors, Opioid/metabolism
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, sigma/agonists
- Receptors, sigma/antagonists & inhibitors
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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24
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Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is a well known inflammatory mediator and algesic substance. It has been hypothesized that 5-HT can have a direct action on peripheral sensory axons, but there has been no anatomical demonstration of 5-HT receptors on peripheral primary afferent processes. The present study shows that 32% of unmyelinated axons at the dermal-epidermal junction are immunohistochemically stained with antibodies directed against the 5-HT2A receptor providing anatomical evidence that 5-HT can have a direct effect on sensory fibers in the skin. Furthermore, encapsulated nerve endings in Pacinian corpuscles also contain reaction product following immunostaining for 5-HT2A receptors, indicating that large myelinated axons can be activated by endogenous serotonin. These data suggest that peripherally acting 5-HT2A antagonists may be effective in reducing pain of peripheral origin.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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25
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Abstract
The dorsal horn of the spinal cord is a primary receiving area for somatosensory input and contains high concentrations of a large variety of receptors. These receptors tend to congregate in lamina II, which is a major receiving center for fine, presumably nociceptive, somatosensory input. There are rapid reorganizations of many of these receptors in response to various stimuli or pathological situations. These receptor localizations in the normal and their changes after various pertubations modify present concepts about the wiring diagram of the nervous system. Accordingly, the present work reviews the receptor localizations and relates them to classic organizational patterns in the mammalian dorsal horn.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555-1069, USA
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26
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Abstract
Cutting or crushing rat sciatic nerve does not significantly reduce the number of central myelinated sensory axons in the dorsal roots entering the fourth and fifth lumbar segments even over very extended periods of time. Unmyelinated axons were reduced by approximately 50%, but only long after sciatic nerve lesions (four to eight months), and reinnervation of the peripheral target did not rescue these axons. This indicates that a peripheral nerve lesion sets up a slowly developing but major shift towards large afferent fiber domination of primary afferent input into the spinal cord. In addition, since myelinated axons are never lost, this is good evidence that the cells that give rise to these fibers are also not lost. If this is the case, this would indicate that adult primary sensory neurons with myelinated axons do not depend on peripheral target innervation for survival.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neurosciences, and Marine Biomedical Institute, The University of Texas Medical Branch, Galveston 77555-1069, USA
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27
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Abstract
The present study demonstrates that local cutaneous administration of either the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist MK-801 or the non-NMDA glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) significantly attenuates formalin-induced nociceptive behaviors. Specifically, pretreatment with either drug reduced the magnitude and time course of lifting and licking behavior in the late phase of formalin pain; however, flinching behavior was not affected. In contrast, post-treatment of formalin pain with either antagonist did not affect lifting and licking behavior, although flinching behavior was mildly attenuated. We hypothesize that these actions result from blocking of peripheral glutamate receptors located on unmyelinated axons at the dermal-epidermal junction. These data suggest that peripheral glutamate receptors on cutaneous axons can be manipulated to reduce certain aspects of pain of peripheral origin. This route of administration offers the advantage of avoiding the side effects of systemic administration.
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Affiliation(s)
- E M Davidson
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, Galveston, TX 77555-1069, USA
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28
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Abstract
Dorsal root ganglia (DRG) contain measurable amounts of met-enkephalin (ENK), and a significant number of DRG cells contain mRNA for the manufacture of ENK. Yet almost no DRG cells are immunostained for ENK and dorsal rhizotomy does not diminish ENK staining in the dorsal horn. A hypothesis which would explain these seemingly discrepant results is the phenomenon of differential transport, where DRG cells making ENK rapidly transport the peptide only to their peripheral sensory axons. Evidence consistent with this hypothesis would be the demonstration of ENK-containing peripheral sensory axons. The present study demonstrates that approximately 17% of peripheral cutaneous axons label for ENK. The presence of a significant number of ENK-containing axons suggests an endogenous neural source of opiate ligand in the periphery and, in addition to ENK-containing inflammatory cells, this neural source may be functionally important in responses to physiologic as well as inflammatory pain.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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29
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Carlton SM, Zhou S, Coggeshall RE. Localization and activation of substance P receptors in unmyelinated axons of rat glabrous skin. Brain Res 1996; 734:103-8. [PMID: 8896815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Immunohistochemical staining for the substance P (neurokinin INK1) receptor labels 32% of the unmyelinated axons in the glabrous skin of the rat hindpaw. This is the first demonstration of substance P (SP) receptors associated with the membranes of primary afferent fibers. Injection of SP into the subcutaneous tissue of the third hind toe results in behavioral changes interpreted as mechanical hyperalgesia and mechanical allodynia. These nocifensive behaviors can be blocked by the NK1 antagonist CP99,994-1. The presence of peripheral axons immunolabelled for NK1 receptors and the demonstration that exogenous peripheral SP causes nocifensive behaviors would seem to indicate that SP can have a direct effect on sensory afferents with activation of these receptors resulting in fine afferent firing and thus the pain-related behaviors. Additionally, the presence of round, clear vesicles in some of the SP receptor-labelled axons suggests the presence of autoreceptors since it is known that many primary sensory afferents contain SP.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555-1069, USA
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30
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Mannion RJ, Doubell TP, Coggeshall RE, Woolf CJ. Collateral sprouting of uninjured primary afferent A-fibers into the superficial dorsal horn of the adult rat spinal cord after topical capsaicin treatment to the sciatic nerve. J Neurosci 1996; 16:5189-95. [PMID: 8756447 PMCID: PMC6579319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/1996] [Revised: 05/30/1996] [Accepted: 06/03/1996] [Indexed: 02/02/2023] Open
Abstract
That terminals of uninjured primary sensory neurons terminating in the dorsal horn of the spinal cord can collaterally sprout was first suggested by Liu and Chambers (1958), but this has since been disputed. Recently, horseradish peroxidase conjugated to the B subunit of cholera toxin (B-HRP) and intracellular HRP injections have shown that sciatic nerve section or crush produces a long-lasting rearrangement in the organization of primary afferent central terminals, with A-fibers sprouting into lamina II, a region that normally receives only C-fiber input (Woolf et al., 1992). The mechanism of this A-fiber sprouting has been thought to involve injury-induced C-fiber transganglionic degeneration combined with myelinated A-fibers being conditioned into a regenerative growth state. In this study, we ask whether C-fiber degeneration and A-fiber conditioning are both necessary for the sprouting of A-fibers into lamina II. Local application of the C-fiber-specific neurotoxin capsaicin to the sciatic nerve has previously been shown to result in C-fiber damage and degenerative atrophy in lamina II. We have used B-HRP to transganglionically label A-fiber central terminals and have shown that 2 weeks after topical capsaicin treatment to the sciatic nerve, the pattern of B-HRP staining in the dorsal horn is indistinguishable from that seen after axotomy, with lamina II displaying novel staining in the identical region containing capsaicin-treated C-fiber central terminals. These results suggest that after C-fiber injury, uninjured A-fiber central terminals can collaterally sprout into lamina II of the dorsal horn. This phenomenon may help to explain the pain associated with C-fiber neuropathy.
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Affiliation(s)
- R J Mannion
- Department of Anatomy and Developmental Biology, University College London, United Kingdom
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31
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Abstract
The present study analyzed the relationships of glycine (GLY)-immunoreactive (-IR) and unlabeled profiles in the primate spinal cord. Light microscopic analysis demonstrated GLY-IR profiles in laminae III-VII, with fewer labeled profiles in laminae I, II, VIII, IX and X. The dorsal part of the lateral funiculus and the dorsal funiculus contained few labeled axons, in contrast to all other areas of white matter, which were heavily labeled. At the electron microscopic level, GLY-IR terminals in monkeys contained mainly round, with occasional pleomorphic, clear vesicles; however, F-type GLY-IR terminals synapsing on motoneurons contained pleomorphic vesicles. This seems to be an important species difference because vesicles in GLY-IR terminals in rat and cat are predominantly oval or elliptical. GLY-IR terminals synapsed on unlabeled as well as GLY-IR cell bodies and dendrites. This is morphological evidence that GLY may be both an inhibitor (GLY-IR terminals synapse on and presumably inhibit non-GLY cell bodies and dendrites) and a disinhibitor (GLY-IR terminals synapse on and presumably inhibit other GLY elements) of spinal activity. Also noteworthy was the conspicuous absence of axoaxonic interactions involving GLY-IR terminals. A related finding was that GLY profiles were always postsynaptic, never presynaptic, to glomerular primary afferent terminals. The functional implications would seem to be that primary afferent input can activate the spinal GLY system but that there is little GLY presynaptic control of afferent input in monkeys. This is in contrast to rats and cats, in which axoaxonic interactions involving GLY-IR terminals have been observed and where it is common to find GLY-IR terminals presynaptic to glomerular primary afferent terminals.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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32
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Abstract
Cholera toxin beta-subunit conjugated to horseradish peroxidase was used to label the large myelinated (A beta) fiber input to the dorsal horn in a model of peripheral neuropathy induced by tight ligation of the L5 and L6 spinal nerves. Following induction of neuropathy, A beta fibers were present in lamina II of the ipsilateral dorsal horn, a region normally devoid of A beta input. This reorganization of large fiber input to the superficial dorsal horn provides some anatomical basis for sensory changes found in this model of neuropathic pain.
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Affiliation(s)
- H A Lekan
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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33
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Coggeshall RE, Jennings EA, Fitzgerald M. Evidence that large myelinated primary afferent fibers make synaptic contacts in lamina II of neonatal rats. Brain Res Dev Brain Res 1996; 92:81-90. [PMID: 8861726 DOI: 10.1016/0165-3806(95)00207-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Choleragenoid horseradish peroxidase (B-HRP) is a retrogradely transported marker that selectively labels large cutaneous myelinated primary afferent fibers. In adults, B-HRP labelled large afferent fibers are seen to enter laminae III-V, and to a lesser extent lamina I, whereas lamina II, which is the major termination site of unmyelinated primary afferents, remains unlabelled. In the neonate, however, there is extensive B-HRP label in lamina II. The present study shows that the B-HRP labelled fibers in the neonate make many synaptic contacts in lamina II. This supports the idea that large primary afferent fibers in neonatal animals make synaptic contact with post-synaptic targets that presumably process nociceptive information. Accordingly to ameliorate pain in neonates it may be more important to block low threshold sensory input whereas in adults it would be more important to block the high threshold inputs.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neuroscience, University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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34
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Abstract
The present study investigates the nature of the galanin (GAL) increase and the calcitonin gene-related peptide (CGRP) decrease in the dorsal horn following peripheral nerve injury. These two peptides are known to colocalize in primary afferent terminals. Primates which had a tight ligation of the L7 spinal nerve demonstrated a variety of neuropathic symptoms 2 weeks postsurgery, including mechanical and cold allodynia, and heat hyperalgesia. Computer-enhanced image analyses of L7 spinal cord sections demonstrated an increase in GAL immunostaining and a decrease in CGRP immunostaining in the experimental compared to the control dorsal horn. Stereological analyses demonstrated that neither the numbers of GAL-labeled synapses nor the numbers or diameters of the dense-core vesicles in each GAL terminal changed after the lesion. However, there was a significant increase in the number of GAL-labeled glial cell bodies and processes on the experimental side, which accounted for the increased staining density observed at the light microscopic level. In contrast, the number of CGRP-labeled terminals was decreased on the experimental side, accounting for the decreased staining density seen at the light level. Thus, the decrease in number of CGRP synapses combined with the stable number of GAL synapses suggests that many GAL terminals no longer colocalize with CGRP after peripheral nerve lesion. This may indicate increased antinociceptive activity after nerve lesions. If so, there is less of a morphologic and more of a functional and chemical plasticity for GAL than may be presently envisioned. The possible role of GAL in neuropathic pain is discussed.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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35
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Abstract
Neuron and synapse numbers are important assays in neuroscience. These numbers are estimated by one of four methods: 1) profile counts, 2) assumption-based methods, 3) serial reconstructions, and 4) stereological methods. The criteria for these methods are diverse. This creates a disparity in that some reviewers accept estimates from any of these methods, while others accept only specific methods. An equally important issue is the diversity of sampling strategies, since unbiased estimates of neuronal or synaptic numbers are contingent upon both counting and sampling techniques. The purpose of this commentary is to institute a dialog that will lead to a better understanding of the strengths and weaknesses of the above methods, and to propose guidelines that should lead to more uniform and thus fairer judging of the studies that provide estimates of neuron or synapse numbers. In addition, adoption of more uniform standards for obtaining unbiased numerical estimates should result in the generation of an unbiased database that will be of considerable use in future studies.
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Affiliation(s)
- R E Coggeshall
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA
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36
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Woolf CJ, Shortland P, Reynolds M, Ridings J, Doubell T, Coggeshall RE. Reorganization of central terminals of myelinated primary afferents in the rat dorsal horn following peripheral axotomy. J Comp Neurol 1995; 360:121-34. [PMID: 7499558 DOI: 10.1002/cne.903600109] [Citation(s) in RCA: 219] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have investigated the time course and extent to which peripheral nerve lesions cause a morphological reorganization of the central terminals of choleragenoid-horseradish peroxidase (B-HRP)-labelled primary afferent fibers in the mammalian dorsal horn. Choleragenoid-horseradish peroxidase is retrogradely transported by myelinated (A) sensory axons to laminae I, III, IV and V of the normal dorsal horn of the spinal cord, leaving lamina II unlabelled. We previously showed that peripheral axotomy results in the sprouting of numerous B-HRP-labelled large myelinated sensory axons into lamina II. We show here that this spread of B-HRP-labelled axons into lamina II is detectable at 1 week, maximal by 2 weeks and persists for over 6 months postlesion. By 9 months, however, B-HRP fibers no longer appear in lamina II. The sprouting into lamina II occurs whether regeneration is allowed (crush) or prevented (section with ligation), and does not reverse at times when peripheral fibers reinnervate the periphery. We also show that 15 times more synaptic terminals in lamina II are labelled by B-HRP 2 weeks after axotomy than in the normal. We interpret this as indicating that the sprouting fibers are making synaptic contacts with postsynaptic targets. This implies that A-fiber terminal reorganization is a prominent and long-lasting but not permanent feature of peripheral axotomy. We also provide evidence that this sprouting is the consequence of a combination of an atrophic loss of central synaptic terminals and the conditioning of the sensory neurons by peripheral axotomy. The sprouting of large sensory fibers into the spinal territory where postsynaptic targets usually receive only small afferent fiber input may bear on the intractable touch-evoked pain that can follow nerve injury.
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Affiliation(s)
- C J Woolf
- Department of Anatomy and Developmental Biology, University College London, England
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37
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Abstract
Immunohistochemical staining for the glutamate receptor subtypes N-methyl-D-aspartate (NMDA), kainate, and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) results in a significant number of labeled unmyelinated axons in the glabrous skin of the rat hindpaw. Injection of glutamate into the rat hindpaw results in behavioral changes interpreted as mechanical allodynia and mechanical hyperalgesia. The anatomical findings provide a reasonable explanation for the action of the exogenous peripheral glutamate, namely that activation of these receptors leads to increased primary afferent activity in unmyelinated axons and thus to pain behaviors. AMPA receptors are frequently associated with small clear vesicles in the axoplasm of the unmyelinated axons, many of which have been previously shown to contain high concentrations of glutamate. This finding indicates that these might be autoreceptors and so glutamate itself might regulate certain types of peripheral impulse traffic. The presence of peripheral glutamate receptors associated with unmyelinated axons suggests the possibility that glutamate antagonists applied peripherally might prevent or attenuate some pain-related behaviors.
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Affiliation(s)
- S M Carlton
- Department of Anatomy and Neurosciences, Marine Biomedical Institute, Galveston, TX 77555-1069, USA
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38
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Coggeshall RE, Pover CM, Fitzgerald M. Dorsal root ganglion cell death and surviving cell numbers in relation to the development of sensory innervation in the rat hindlimb. Brain Res Dev Brain Res 1994; 82:193-212. [PMID: 7842509 DOI: 10.1016/0165-3806(94)90163-5] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study correlates the numbers of dying, surviving and proliferating L4 primary afferent neurons with the development of peripheral hindlimb sensory innervation in the rat. Cell death occurs from embryonic day 15 (E15) to just after birth and peaks at E17-E19. Despite this, surviving cell numbers rise steadily to birth indicating that cell death is more than balanced by cell proliferation over this period. GAP-43 immunostaining indicates that the peripheral sensory axons are only in central parts of the hindlimb by E15 and do not finish arriving at their distal peripheral targets until birth so prenatal cell death in the L4 ganglion is not well correlated with the development of the peripheral innervation by these primary sensory axons. Prenatal cell death does, however, correlate well with the innervation of the cord by central sensory axons. In contrast to the steady rise of surviving cell numbers from E15 to birth, cell numbers go down 16% in the period from birth to postnatal day 5. This loss is correlated with the development of the peripheral innervation. We conclude that the bulk of cell death in the rat L4 dorsal root ganglion, which is prenatal, is controlled by local or central factors whereas peripheral target factors may exert their influence postnatally to determine the final numbers of mammalian sensory neurons. The data also suggest that there may be two phases of cell death, an early phase involving large light cells and a late phase involving small dark cells.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy, University of Texas Medical Branch, Galveston 77555-0843
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39
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Chong MS, Reynolds ML, Irwin N, Coggeshall RE, Emson PC, Benowitz LI, Woolf CJ. GAP-43 expression in primary sensory neurons following central axotomy. J Neurosci 1994; 14:4375-84. [PMID: 8027785 PMCID: PMC6577027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Primary sensory neurons are capable of successful regenerative growth in response to peripheral nerve but not dorsal root injury. The present study is concerned with the differential expression of the mRNA for GAP-43, a growth-associated protein, in these sensory neurons, in response to injury of their central or peripheral axonal branches. Peripheral axotomy resulted in an elevation in message detectable within 24 hr, using Northern blot and in situ hybridization, which was maintained for 30 d, whereas dorsal root section produced no change except a transient and small increase if the axotomy was immediately adjacent to the dorsal root ganglia (DRG). Dorsal root section had no effect on GAP-43 mRNA levels in the dorsal horn or in neighboring intact DRG. It also failed to alter the laminar boundaries of the GAP-43 central terminal labeling produced by peripheral nerve section, even though vacant synaptic sites were produced in unstained laminae by this procedure. This indicates that the location of GAP-43 immunolabeling in the central terminals of primed sensory cells may not depend only on the location of vacant synaptic sites. We conclude that distinct control mechanisms regulate the response of DRG neurons to peripheral nerve and dorsal root injury, and these may be related both to the glial environment and the particular target influences exerted on the central and peripheral branches of the primary sensory neuron. Central denervation alone is insufficient to upregulate GAP-43 levels, and this may explain the relative absence of collateral sprouting after the production of central vacant synaptic sites. The failure of dorsal root section to increase GAP-43 expression may contribute to the poor regenerative response initiated by such lesions.
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Affiliation(s)
- M S Chong
- Department of Anatomy and Developmental Biology, University College London, United Kingdom
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40
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Abstract
Adult mammalian primary afferent neurogenesis implies considerably more plasticity for the adult nervous system than is presently envisioned. One hypothesis is that such neurogenesis does not occur, because no tritiated-thymidine-labeled or mitosing neurons are observed in adults, and no increase in cells can be found in young as compared to old adults. The other hypothesis is that adult primary afferent neurogenesis does occur, but that it has not been observed because it is correlated with changes in the size of the animals. This has not been tested, and because of the implications of adult neurogenesis, it is important to see whether dorsal root ganglion (DRG) cell numbers increase with animal size. This is particularly pertinent because of recent advances in the technology for counting neurons and improved methods for resolving the cells in question. The present results indicate that DRG cell numbers are approximately the same in animals whose sizes are different by a factor of approximately 5. Thus our data are consistent with the hypothesis that numbers of adult DRG cells are stable, and we cannot demonstrate a change in relation to age or body size in our animals. Therefore, we do not find evidence of adult neurogenesis in our animals.
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Affiliation(s)
- C M Pover
- Department of Anatomy and Neuroscience, University of Texas Medical Branch, Galveston 77555-0843
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41
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Abstract
An important goal in neuroscience is to produce frequency distribution curves or histograms that relate numbers of cells to their sizes. Unfortunately such histograms, which are extremely common, are biased. Some of the reasons are inadequate attention to sampling paradigms, the lack of assurance that the section through the center of the cell is measured, and that large cells will have more profiles than small cells. The first goal of this paper is to illustrate these biases for dorsal root ganglion cells by showing significant statistical differences between histograms prepared the classic way and histograms produced by unbiased methods. The differences are particularly dramatic for plastic embedded material. The second goal of the paper is to describe an unbiased method for obtaining these histograms. The procedure is 2-fold. Cells are chosen in an unbiased way (unbiased in this sense means that every cell has an equal chance of being chosen), and then the largest profile of the cell is measured. We further suggest that these histograms be accompanied by analyses of cell volume, since volumes of cells rather than diameters or areas of cell profiles, will be the future measure of choice when considering the sizes of cells (or any other particles of biologic interest).
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Affiliation(s)
- C M Pover
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555
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42
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Abstract
Cell death or apoptosis is regarded as an important feature of mammalian neural development, but the evidence for this generalization depends on the assumption that cell death can be clearly recognized. The usual profile of a dying neuron is a deeply stained pyknotic homogeneous sphere. In this paper we present evidence that such profiles in embryonic rat T6 and L4 dorsal root ganglia are not dying neurons but rather nuclei of immature red blood cells. This observation, combined with recent work showing that the methods previously used for counting normal or dying neurons are biased, indicates that the classic work establishing the importance of apoptosis needs to be repeated.
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston
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Abstract
Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given L-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5% glutaraldehyde, 4% paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 microns. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.
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Affiliation(s)
- K N Westlund
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77550
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Klein CM, Coggeshall RE, Carlton SM, Sorkin LS. The effects of A- and C-fiber stimulation on patterns of neuropeptide immunostaining in the rat superficial dorsal horn. Brain Res 1992; 580:121-8. [PMID: 1504792 DOI: 10.1016/0006-8993(92)90935-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study determines the effects of sciatic nerve stimulation at intensities that activate A-fibers alone or both A- and C-fibers on immunostaining for substance P (SP), cholecystokinin-octapeptide (CCK-8), galanin (GAL), dynorphin (DYN) and vasoactive intestinal polypeptide (VIP) in the superficial dorsal horn of the rat spinal cord. The goal of this study is to provide a more precise spatial localization of the sites of release or accumulation of these compounds in relation to specific types of stimuli. Following A-fiber stimulation, there was no significant change in immunostaining for any of these compounds. However, A- and C-fiber stimulation resulted in major changes. For SP, CCK-8, GAL and DYN there was a large and significant loss of immunostaining in medial regions of the dorsal horn. This is the area where sciatic nerve primary afferent fibers terminate and the depletion is probably correlated with activity in these fibers. By contrast, VIP immunostaining is increased in the lateral part of the superficial cord, which is outside of the central sciatic afferent fiber terminations. This indicates that the increase is not in the fine sciatic sensory axons that are directly stimulated. As a final point, the fact that C-fiber but not A-fiber stimulation causes marked changes in the immunocytochemical distribution of all these compounds is further evidence, albeit indirect, that they are involved in nociceptive information processing.
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Affiliation(s)
- C M Klein
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77550
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Cameron AA, Pover CM, Willis WD, Coggeshall RE. Evidence that fine primary afferent axons innervate a wider territory in the superficial dorsal horn following peripheral axotomy. Brain Res 1992; 575:151-4. [PMID: 1504776 DOI: 10.1016/0006-8993(92)90436-d] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Peripheral axotomy initiates changes in central primary afferent receiving areas of the dorsal horn of the spinal cord. Most of the presently known changes are degenerative in nature and consist of such things as cell and axon death or declines in peptides or enzymes. Other changes are regenerative in nature and because most of these occur in the superficial dorsal horn, which is where fine primary afferents end, we wished to ask whether peripheral axotomy results in a change in the distribution in these fine afferents. Using recently available markers for fine primary afferent axons and small dorsal root ganglion cells, we demonstrate that peripheral axotomy results in a considerable increase in the immunolabeled area for these compounds. Our interpretation is that there may be an extension of fine primary afferent fibers into lamina III and possibly lamina IV following peripheral axotomy. If further work bears out this conclusion, this would provide a possible explanation for the chronic pain states that sometimes follow peripheral nerve damage.
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Affiliation(s)
- A A Cameron
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77550
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Garrett L, Coggeshall RE, Patterson JT, Chung K. Numbers and proportions of unmyelinated axons at cervical levels in the fasciculus gracilis of monkey and cat. Anat Rec (Hoboken) 1992; 232:301-4. [PMID: 1546808 DOI: 10.1002/ar.1092320215] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study is a quantitative analysis of the unmyelinated fiber population in the fasciculus gracilis of the second cervical segment of cat and monkey. We find that unmyelinated fibers represent 13.7% of the total fiber population in this pathway in the cat and 18.9% in the monkey (Macaca fascicularis). The existence of such large numbers of these axons suggests that there may be a sizeable ascending fine primary afferent pathway in the fasciculus gracilis in cat and monkey whose destination is presumably the dorsal column nuclei. These findings are of interest in regard to classic ideas that the afferent fibers in the dorsal columns are large myelinated fibers that convey fine discriminative information to the dorsal column nuclei.
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Affiliation(s)
- L Garrett
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston
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47
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Abstract
The central terminals of primary afferent neurons are topographically highly ordered in the spinal cord. Peripheral receptor sensitivity is reflected by dorsal horn laminar location: low-threshold mechanoreceptors terminate in laminae III and IV (refs 2, 3) and high-threshold nociceptors in laminae I, II and V (refs 4,5). Unmyelinated C fibres, most of which are nociceptors, terminate predominantly in lamina II (refs 5, 7). There is therefore an anatomical framework for the transfer of specific inputs to localized subsets of dorsal horn neurons. This specificity must contribute to the relationship between a low-intensity stimulus and an innocuous sensation and a noxious stimulus and pain. We now show that after peripheral nerve injury the central terminals of axotomized myelinated afferents, including the large A beta fibres, sprout into lamina II. This structural reorganization in the adult central nervous system may contribute to the development of the pain mediated by A-fibres that can follow nerve lesions in humans.
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Affiliation(s)
- C J Woolf
- Department of Anatomy and Developmental Biology, University College London
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48
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Abstract
It is often necessary to obtain unbiased estimates of neuronal or synaptic numbers. In the past, estimates were almost always done by counting profiles of these structures in single histological sections. Assumptions were then made and calculations were done to determine particle numbers or ratios. To the extent that the assumptions deviated from reality, the conclusions will be biased. That these biases are, in fact, serious has recently become apparent. To obtain unbiased particle counts, the presently available methods are serial-section reconstructions (which are accurate but cumbersome), and the recently developed disector method. The disector method, because it is unbiased and easy to use, is becoming the method of choice. The goals of this paper are to show why previous methods are biased and to describe the rationale behind the disector method so that neuroscientists can consider its appropriateness for their work.
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Klein CM, Sorkin LS, Chung K, Coggeshall RE. Unmyelinated primary afferent fiber stimulation depletes dynorphin A (1-8) immunoreactivity in rat ventral horn. Brain Res 1991; 566:70-6. [PMID: 1687665 DOI: 10.1016/0006-8993(91)91682-q] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The present study demonstrates many dynorphin (DYN)-immunoreactive fibers and presumed presynaptic terminals in rat lumbar ventral horn. The fibers and terminals seem to arise largely from DYN-containing intrinsic neurons in the dorsal horn. The majority of the presumed terminals closely surround a subpopulation of motoneurons that tend to be located in flexor motoneuron columns. Acute C fiber, but not A fiber, primary afferent stimulation depletes the ventral horn DYN immunostaining. We interpret these findings to indicate that the spinal DYN neurons are well positioned to serve both as modulators of nociceptive input and as interneurons in motor reflexes. We further hypothesize that the depletion of DYN-immunoreactivity that follows either acute C fiber stimulation or intense nociceptive stimuli may be the trigger for the upregulation in spinal cord DYN that occurs in models of chronic pain states.
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Affiliation(s)
- C M Klein
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77550
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50
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Affiliation(s)
- R E Coggeshall
- Department of Anatomy and Neuroscience, University of Texas Medical Branch, Galveston 77550
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