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Coggeshall RE, Lekan HA, Doubell TP, Allchorne A, Woolf CJ. Central changes in primary afferent fibers following peripheral nerve lesions. Neuroscience 1997; 77:1115-22. [PMID: 9130791 DOI: 10.1016/s0306-4522(96)00528-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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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Davidson EM, Coggeshall RE, Carlton SM. Peripheral NMDA and non-NMDA glutamate receptors contribute to nociceptive behaviors in the rat formalin test. Neuroreport 1997; 8:941-6. [PMID: 9141069 DOI: 10.1097/00001756-199703030-00025] [Citation(s) in RCA: 158] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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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Carlton SM, Coggeshall RE. Immunohistochemical localization of enkephalin in peripheral sensory axons in the rat. Neurosci Lett 1997; 221:121-4. [PMID: 9121679 DOI: 10.1016/s0304-3940(96)13304-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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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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] [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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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] [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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Carlton SM, Hargett GL, Coggeshall RE. Distribution of glycine-immunoreactive profiles in the monkey spinal cord: a light microscopic and ultrastructural study. J Comp Neurol 1996; 371:589-602. [PMID: 8841912 DOI: 10.1002/(sici)1096-9861(19960805)371:4<589::aid-cne8>3.0.co;2-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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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Lekan HA, Carlton SM, Coggeshall RE. Sprouting of A beta fibers into lamina II of the rat dorsal horn in peripheral neuropathy. Neurosci Lett 1996; 208:147-50. [PMID: 8733291 DOI: 10.1016/0304-3940(96)12566-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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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Coggeshall RE, Jennings EA, Fitzgerald M. Evidence that large myelinated primary afferent fibers make synaptic contacts in lamina II of neonatal rats. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 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] [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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Carlton SM, Coggeshall RE. Stereological analysis of galanin and CGRP synapses in the dorsal horn of neuropathic primates. Brain Res 1996; 711:16-25. [PMID: 8680859 DOI: 10.1016/0006-8993(95)01303-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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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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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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] [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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Carlton SM, Hargett GL, Coggeshall RE. Localization and activation of glutamate receptors in unmyelinated axons of rat glabrous skin. Neurosci Lett 1995; 197:25-8. [PMID: 8545047 DOI: 10.1016/0304-3940(95)11889-5] [Citation(s) in RCA: 268] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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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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 RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 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] [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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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] [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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Pover CM, Barnes MC, Coggeshall RE. Do primary afferent cell numbers change in relation to increasing weight and surface area in adult rats? Somatosens Mot Res 1994; 11:163-7. [PMID: 7976010 DOI: 10.3109/08990229409028869] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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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Pover CM, Orr MH, Coggeshall RE. A method for producing unbiased histograms of neuronal profile sizes. J Neurosci Methods 1993; 49:123-31. [PMID: 8271825 DOI: 10.1016/0165-0270(93)90116-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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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Coggeshall RE, Pover CM, Kwiat GC, Fitzgerald M. Erythrocyte nuclei resemble dying neurons in embryonic dorsal root ganglia. Neurosci Lett 1993; 157:41-4. [PMID: 8233029 DOI: 10.1016/0304-3940(93)90638-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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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Westlund KN, Lu Y, Coggeshall RE, Willis WD. Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys. Neurosci Lett 1992; 141:35-8. [PMID: 1508397 DOI: 10.1016/0304-3940(92)90328-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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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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] [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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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] [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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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] [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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Woolf CJ, Shortland P, Coggeshall RE. Peripheral nerve injury triggers central sprouting of myelinated afferents. Nature 1992; 355:75-8. [PMID: 1370574 DOI: 10.1038/355075a0] [Citation(s) in RCA: 837] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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] [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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Coggeshall RE. Verification of the Devor et al. (1985) method of determining neural numbers. J Neurosci Methods 1991; 40:87-90. [PMID: 1686924 DOI: 10.1016/0165-0270(91)90056-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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