Effect of peripheral axotomy on pain-related behavior and dorsal root ganglion neurons excitability in NPY transgenic rats (original) (raw)
Related papers
NT-3 modulates NPY expression in primary sensory neurons following peripheral nerve injury
Journal of Anatomy, 1998
Peripheral nerve transection induces significant changes in neuropeptide expression and content in injured primary sensory neurons, possibly due to loss of target derived neurotrophic support. This study shows that neurotrophin-3 (NT-3) delivery to the injured nerve influences neuropeptide Y (NPY) expression within dorsal root ganglia (DRG) neurons. NT-3 was delivered by grafting impregnated fibronectin (500 ng\ml ; NT group) in the axotomised sciatic nerve. Animals grafted with plain fibronectin mats (FN) or nerve grafts (NG) were used as controls. L4 and L5 DRG from operated and contralateral sides were harvested between 5 and 240 d. Using immunohistochemistry and computerised image analysis the percentage, diameter and optical density of neurons expressing calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP) and NPY were quantified. Sciatic nerve axotomy resulted in significant reduction in expression of CGRP and SP, and significant upregulation of VIP and NPY (P 0n05 for ipsilateral vs contralateral DRG). By d 30, exogenous NT-3 and nerve graft attenuated the upregulation of NPY (P 0n05 for NT and NG vs FN). However, NT-3 administration did not influence the expression of CGRP, SP or VIP. The mean cell diameter of NPY immunoreactive neurons was significantly smaller in the NT-3 group (P 0n05 for NT vs FN and NG) suggesting a differential influence of NT-3 on larger neurons. The optical densities of NPY immunoreactive neurons of equal size were the same in each group at any time point, indicating that the neurons responding to NT-3 downregulate NPY expression to levels not detectable by immunohistochemistry. These results demonstrate that targeted administration of NT-3 regulates the phenotype of a NPY-immunoreactive neuronal subpopulation in the dorsal root ganglia, a further evidence of the trophic role of neurotrophins on primary sensory neurons.
Pain, 1999
Recent animal models of experimental nerve injury have proven useful in evaluating potential sympathetic involvement in neuropathic pain syndromes. We have employed a widely adopted unilateral L 5 /L 6 spinal nerve ligation model to compare the development of mechanical allodynia with neurochemical changes both at the site of peripheral nerve injury and in the dorsal root ganglia (DRG). We have focused on the expression of neuropeptide Y (NPY), a well-studied regulatory peptide and phenotypic marker of sympathetic neurons, and functionally related Y-receptor binding sites following nerve injury. In sympathetic neurons, NPY is colocalized and coreleased with norepinephrine (NE) at peripheral sites of action. Furthermore, NPY gene expression is induced within the population of medium-and large-diameter DRG neurons of the Ab-fiber class after experimental nerve injury. We therefore hypothesized that concurrent alterations in NPY and NE expression by sympathetic and sensory neurons may be a contributing factor to sympathetically-maintained neuropathic conditions. Animals with unilateral L 5 /L 6 spinal nerve ligation developed mechanical allodynia of the hind paw ipsilateral to the site of injury that persisted until sacrifice at postoperative day 10. A significant induction of preproneuropeptide Y-encoding (PPNPY) mRNA, as detected by in situ hybridization histochemistry (ISHH), occurred in populations of medium-and large-diameter DRG neurons ipsilateral to the site of injury. Immunohistochemical analysis indicated a marked decline in the number of labeled sympathetic axons positive for tyrosine hydroxylase-like and NPY-like immunoreactivities (TH-Ll and NPY-LI, respectively) proximal to the site of nerve injury and almost complete elimination of immunopositive fibers distal to the site of ligation. Whereas, the extent of colocalization of NPY-LI to TH-LI-positive sympathetic axons in unaffected L 4 or L 5 nerve segments exceeded 80%, this figure declined to approximately 50% in regenerating axons of ligated spinal nerve L 5. The portion of NPY-LI that was not colocalized to sympathetic TH-LI-positive fibers was most likely contributed by regenerating sensory axons, consistent with marked de novo synthesis of NPY by DRG neurons. In end bulb axon terminals, i.e. morphological profiles characteristic of neuromas, NPY-LI-positive elements that were not colocalized to TH-LI-positive sympathetic elements appeared to be spatially segregated from those of sympathetic origin with colocalized TH-LI and NPY-LI. Receptor autoradiography indicated that smalland medium-diameter DRG somata of the C-fiber class normally express both Y 1 and Y 2 receptor subtypes. The pattern of the distribution of Y-receptor binding sites appeared to be relatively unaffected by spinal nerve ligation. In contrast, there was a marked increase in the density of Y 2 receptor binding sites in the proximal segment of ligated spinal nerve L 5 , consistent with previously published data indicating differential transport of the Y 2 autoregulatory receptor subtype to nerve terminals. Induction of NPY gene expression in injured DRG neurons is consistent with appearance of NPY-LI-positive end bulbs derived from regenerating sensory axons that are found in developing neuromas containing a relatively high density of transported prejunctional Y 2 receptors. Newly established functional interactions of spatially segregated sensory-and sympathetically-derived end bulbs in developing neuromas may enhance neuronal hyperexcitability engendered by aberrant electrical activity at the site of injury. Injury-related alterations in the regulatory activities of NPY released within the DRG at somally-distributed Y-receptors may also contribute to the development and/or persistence of symptoms characteristic of sympatheticallymaintained pain. Finally, at later times NPY-mediated modulation of NE release from invading sympathetic axon terminals within the DRG may affect the extent of a 2 receptor-mediated neuronal hyperexcitability associated with neuropathic pain.
Neuroscience, 1999
Abstrac~Damage to sensory nerves invokes the expression of neuropeptide Y in the cell bodies of sensory neurons in dorsal root ganglia. We therefore compared the action of this peptide on control dorsal root ganglia neurons with its action on neurons from animals in which the sciatic nerve had been cut. Neuropeptide Y (0.1-1.0 gM) increased the excitability of 24% of control neurons and its effect was stronger and more cells (56%) were affected after axotomy. Increased excitability was mediated via a Yz-receptor and resulted from attenuation of CaZ+-sensitive K+-conductance(s) secondary to suppression of N-type Ca 2÷ channel current. Yl-agonists potentiated L-type Ca 2÷ channel current in control neurons without altering excitability. This Y~-effect was attenuated whereas effects mediated via Yz-receptors were enhanced after axotomy. No evidence was found for involvement of Y4" or Ys-receptor subtypes in the aclions of neuropeptide Y either on control or on axotomized dorsal root ganglion neurons. It is concluded that neuropeptide Y increases the excitability of sensory neurons by interacting with a Yz-receptor and thereby decreasing N-type Ca 2+ channel current and Ca2+-sensitive K+-conductance(s). When peripheral nerves are damaged, dorsal root ganglion neurons start to express neuropeptide Y and its excitatory Y2-excitatory effects are enhanced. The peptide may therefore contribute to the generation of aberrant sensory activity and perhaps to the etiology of injury-induced neuropathic pain. C~ 1998 IBRO. Published by Elsevier Science Ltd.
European Journal of Neuroscience, 2004
Peripheral tissue injury-induced central sensitization may result from the altered biochemical properties of spinal dorsal horn. However, peripheral nerve injury-induced modi®cation of genes in the dorsal horn remains largely unknown. Here we identi®ed strong changes of 14 channels, 25 receptors and 42 signal transduction related molecules in Sprague±Dawley rat dorsal spinal cord 14 days after peripheral axotomy by cDNA microarray. Twenty-nine genes were further con®rmed by semiquantitative RT-PCR, Northern blotting, in situ hybridization and immunohistochemistry. These regulated genes included Ca 2 channel a1E and a2/d1 subunits, a subunits for Na channel 1 and 6, Na channel b subunit, AMAP receptor GluR3 and 4, GABA A receptor a5 subunit, nicotinic acetylcholine receptor a5 and b2 subunits, PKC a, bI and d isozymes, JNK1±3, ERK2±3, p38 MAPK and BatK and Lyn tyrosine-protein kinases, indicating that several signal transduction pathways were activated in dorsal spinal cord by peripheral nerve injury. These results demonstrate that peripheral nerve injury causes phenotypic changes in spinal dorsal horn. Increases in Ca 2 channel a2/d1 subunit, GABA A receptor a5 subunit, Na channels and nicotinic acetylcholine receptors in both dorsal spinal cord and dorsal root ganglia indicate their potential roles in neuropathic pain control.
Biomedicines
Background: Somatic nerve injuries are a rising problem leading to disability associated with neuropathic pain commonly reported as mechanical allodynia (MA) and hyperalgesia. These symptoms are strongly dependent on specific processes in the dorsal root ganglia (DRG). Neurodynamic treatment (NDT), consisting of selective uniaxial nerve repeated tension protocols, effectively reduces pain and disability in neuropathic pain patients even though the biological mechanisms remain poorly characterized. We aimed to define, both in vivo and ex vivo, how NDT could promote nerve regeneration and modulate some processes in the DRG linked to MA and hyperalgesia. Methods: We examined in Wistar rats, after unilateral median and ulnar nerve crush, the therapeutic effects of NDT and the possible protective effects of NDT administered for 10 days before the injury. We adopted an ex vivo model of DRG organotypic explant subjected to NDT to explore the selective effects on DRG cells. Results: Behavio...
Neuroscience, 2001
AbstractöSeveral types of changes have been reported to occur in dorsal root ganglia following peripheral nerve injury, including loss of neurons and increases and decreases in peptide expression. However, with regard to loss of neurons, results have not been consistent, presumably due to di¡erent quantitative methodologies employed and species analyzed. So far, most studies have been conducted on rats; however, with the fast development of the transgenic techniques, the mouse has become a standard model animal in primary sensory research. Therefore we used stereological methods to determine the number of neurons, as well as the expression of galanin message-associated peptide, a marker for galaninexpressing neurons, neuropeptide Y, and calcitonin gene-related peptide in lumbar 5 dorsal root ganglia of both control C57 BL/6J mice and in mice subjected to a`mid-thigh' sciatic nerve transection (axotomy).
Proceedings of the National Academy of Sciences of the United States of America, 1997
The effect of three peptides, galanin, sulfated cholecystokinin octapeptide, and neurotensin (NT), was studied on acutely extirpated rat dorsal root ganglia (DRGs) in vitro with intracellular recording techniques. Both normal and peripherally axotomized DRGs were analyzed, and recordings were made from C-type (small) and A-type (large) neurons. Galanin and sulfated cholecystokinin octapeptide, with one exception, had no effect on normal C-and A-type neurons but caused an inward current in both types of neurons after sciatic nerve cut. In normal rats, NT caused an outward current in C-type neurons and an inward current in A-type neurons. After sciatic nerve cut, NT only caused an inward current in both C-and A-type neurons. These results suggest that (i) normal DRG neurons express receptors on their soma for some but not all peptides studied, (ii) C-and A-type neurons can have different types of receptors, and (iii) peripheral nerve injury can change the receptor phenotype of both C-and A-type neurons and may have differential effects on these neuron types.
NPY Y1 Receptors Are Present in Axonal Processes of DRG Neurons
Experimental Neurology, 2002
Using a sensitive immunohistochemical method, the localization of the neuropeptide Y (NPY) Y1 receptor (Y1R) was studied in contralateral and ipsilateral dorsal root ganglion (DRG) neurons of rats subjected to different unilateral manipulations with focus on their axonal processes and projection areas. Y1R-like immunoreactivity (LI) was observed in the contralateral sciatic nerve and dorsal roots of lesioned rats, and double staining revealed colocalization with calcitonin generelated peptide (CGRP). Y1R-LI was also seen in fibers close to and even within the epidermis. A fairly small number of nerve endings double-labeled for Y1R and CGRP were present in the dorsal horn. After unilateral crush of the sciatic nerve Y1R-and CGRP-LI accumulated in the same axons proximal to the lesion. After dorsal rhizotomy CGRP-LI was strongly reduced in the ipsilateral dorsal horn. No certain change was observed for Y1R-or NPY-LI, but Y1R/CGRP doublelabeled nerve endings disappeared after the lesion. These results strongly suggest centrifugal transport of Y1Rs in DRG neurons, mainly to the peripheral sensory branches. To what extent these Y1Rs are functional has not been analyzed here, but a recent study on Y1R null mice provides evidence for involvement of prejunctional Y1Rs in peripheral sensory functions
Regulatory Peptides, 1998
The lumbar 5 (L5) dorsal root ganglia (DRGs) were studied in neuropeptide tyrosine (NPY)-deficient (2 / 2) and wild type (1 / 1) mice after unilateral sciatic nerve transection using in situ hybridization and immunohistochemistry. NPY, galanin and two NPY receptors (Y-Rs) were analyzed as well as self-mutilation behaviour (autotomy) and nociceptive thresholds. No difference between wild type and NPY-deficient mice was seen in the tail-flick or hot plate test. However, 2 / 2 mice showed a much stronger autotomy behaviour than wild type mice. NPY was not found in L5 DRGs in 2 / 2 mice, not even after axotomy. Galanin was upregulated to the same extent after axotomy in NPY-deficient and wild type mice. Y1-and Y2-R mRNAs were found mainly in small DRG neuron profiles. Both receptor mRNAs were downregulated after axotomy, to about the same extent in NPY-deficient as in wild type mice. In control and contralateral ganglia the mRNA levels of both receptors were lower in NPY-deficient mice than in wild type mice. The contralateral Y2-R mRNA levels did not reach control values in the NPY-deficient mice, as they did in the wild type mice. In both strains the Y1-R protein was decorating the somatic plasmalemma. The present results suggest that lack of NPY may cause exaggerated autotomy, a self-mutilation behaviour possibly related to pain sensation, in agreement with the described analgesic effect of NPY. Although significant differences in levels of Y1-and especially Y2-R mRNAs were observed between wild type and NPY-deficient mice, they were only moderate. These findings suggest that expression, regulation, localization and possible function of Y1-and Y2-Rs are not dependent on presence of the endogenous ligand. Also, deletion of NPY does not seem to influence the expression of the partly coexisting peptide galanin.
Journal of …, 2003
We investigated electrophysiological changes in chronically axotomized and neighboring intact dorsal root ganglion (DRG) neurons in rats after either a peripheral axotomy consisting of an L5 spinal nerve ligation (SNL) or a central axotomy produced by an L5 partial rhizotomy (PR). SNL produced lasting hyperalgesia to punctate indentation and tactile allodynia to innocuous stroking of the foot ipsilateral to the injury. PR produced ipsilateral hyperalgesia without allodynia with recovery by day 10. Intracellular recordings were obtained in vivo from the cell bodies (somata) of axotomized and intact DRG neurons, some with functionally identified peripheral receptive fields. PR produced only minor electrophysiological changes in both axotomized and intact somata in L5 DRG. In contrast, extensive changes were observed after SNL in large- and medium-sized, but not small-sized, somata of intact (L4) as well as axotomized (L5) DRG neurons. These changes included (in relation to sham values) higher input resistance, lower current and voltage thresholds, and action potentials with longer durations and slower rising and falling rates. The incidence of spontaneous activity, recorded extracellularly from dorsal root fibers in vitro, was significantly higher (in relation to sham) after SNL but not after PR, and occurred in myelinated but not unmyelinated fibers from both L4 (9.1%) and L5 (16.7%) DRGs. We hypothesize that the changes in the electrophysiological properties of axotomized and intact DRG neurons after SNL are produced by a mechanism associated with Wallerian degeneration and that the hyperexcitability of intact neurons may contribute to SNL-induced hyperalgesia and allodynia.