1
|
Bai Y, Li MY, Ma JB, Li JN, Teng XY, Chen YB, Yin JB, Huang J, Chen J, Zhang T, Qiu XT, Chen T, Li H, Wu SX, Peng YN, Li X, Kou ZZ, Li YQ. Enkephalinergic Circuit Involved in Nociceptive Modulation in the Spinal Dorsal Horn. Neuroscience 2020; 429:78-91. [PMID: 31917345 DOI: 10.1016/j.neuroscience.2019.12.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 11/24/2022]
Abstract
Enkephalin (ENK) has been implicated in pain modulation within the spinal dorsal horn (SDH). Revealing the mechanisms underlying ENK analgesia entails the anatomical and functional knowledge of spinal ENK-ergic circuits. Herein, we combined morphological and electrophysiological studies to unravel local ENK-ergic circuitry within the SDH. First, the distribution pattern of spinal ENK-ergic neurons was observed in adult preproenkephalin (PPE)-GFP knock-in mice. Next, the retrograde tracer tetramethylrhodamine (TMR) or horseradish peroxidase (HRP) was injected into the parabrachial nucleus (PBN) in PPE-GFP mice. Immunofluorescent staining showed I-isolectin B4 (IB4) labeled non-peptidergic afferents were in close apposition to TMR-labeled PBN-projecting neurons within lamina I as well as PPE-immunoreactivity (-ir) neurons within lamina II. Some TMR-labeled neurons were simultaneously in close association with both IB4 and PPE-ir terminals. Synaptic connections of these components were further confirmed by electron microscopy. Finally, TMR was injected into the PBN in adult C57BL/6 mice. Whole-cell patch recordings showed that δ-opioid receptor (DOR) agonist, [D-Pen2,5]-enkephalin (DPDPE, 1 µM), significantly reduced the frequency of miniature excitatory postsynaptic current (mEPSC) and decreased the activity of TMR-labeled neurons. In conclusion, spinal ENKergic neurons receive direct excitatory inputs from primary afferents, which might be directly recruited to release ENK under the condition of noxious stimuli; ENK could inhibit the glutamatergic transmission towards projecting neurons via presynaptic and postsynaptic DORs. These morphological and functional evidence may explain the mechanisms underlying the analgesic effects exerted by ENK within the SDH.
Collapse
Affiliation(s)
- Yang Bai
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Meng-Ying Li
- Department of Endocrinology and Metabolism, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Jiang-Bo Ma
- Department of Anatomy, Histology and Embryology, Ningxia Medical University, Yinchuan, China
| | - Jia-Ni Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Xiao-Yu Teng
- Department of Anatomy, Guangxi Medical University, Nanning, China
| | - Ying-Biao Chen
- Department of Anatomy, Fujian Health College, Fuzhou, China
| | - Jun-Bin Yin
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Jing Huang
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Jing Chen
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Ting Zhang
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Xin-Tong Qiu
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Tao Chen
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Hui Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Sheng-Xi Wu
- Department of Neurobiology, The Fourth Military Medical University, Xi'an, China
| | - Ya-Nan Peng
- Joint Laboratory of Neuroscience at Hainan Medical University and The Fourth Military Medical University, Hainan Medical University, Haikou, China
| | - Xiang Li
- Department of Orthopaedics, The First Affiliated Hospital, Nanjing Medical University, Nanjing, China.
| | - Zhen-Zhen Kou
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China.
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China; Joint Laboratory of Neuroscience at Hainan Medical University and The Fourth Military Medical University, Hainan Medical University, Haikou, China.
| |
Collapse
|
2
|
Peptidergic nature of nociception-related projections from the hypothalamic paraventricular nucleus to the dorsal horn of the spinal cord. Neurosci Lett 2018; 685:124-130. [DOI: 10.1016/j.neulet.2018.08.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 08/07/2018] [Accepted: 08/14/2018] [Indexed: 11/23/2022]
|
3
|
White HD, Robinson TD. A novel use for testosterone to treat central sensitization of chronic pain in fibromyalgia patients. Int Immunopharmacol 2015; 27:244-8. [DOI: 10.1016/j.intimp.2015.05.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/27/2015] [Accepted: 05/11/2015] [Indexed: 11/27/2022]
|
4
|
Abstract
Nociceptors and neurons in the central nervous system (CNS) that receive nociceptive input show remarkable plasticity in response to injury. This plasticity is thought to underlie the development of chronic pain states. Hence, further understanding of the molecular mechanisms driving and maintaining this plasticity has the potential to lead to novel therapeutic approaches for the treatment of chronic pain states. An important concept in pain plasticity is the presence and persistence of "hyperalgesic priming." This priming arises from an initial injury and results in a remarkable susceptibility to normally subthreshold noxious inputs causing a prolonged pain state in primed animals. Here we describe our current understanding of how this priming is manifested through changes in signaling in the primary nociceptor as well as through memory like alterations at CNS synapses. Moreover, we discuss how commonly utilized analgesics, such as opioids, enhance priming therefore potentially contributing to the development of persistent pain states. Finally we highlight where these priming models draw parallels to common human chronic pain conditions. Collectively, these advances in our understanding of pain plasticity reveal a variety of targets for therapeutic intervention with the potential to reverse rather than palliate chronic pain states.
Collapse
Affiliation(s)
- Ram Kandasamy
- Department of Pharmacology, The University of Arizona, Tucson, AZ, 85721, USA
| | | |
Collapse
|
5
|
Price TJ, Inyang KE. Commonalities between pain and memory mechanisms and their meaning for understanding chronic pain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 131:409-34. [PMID: 25744681 DOI: 10.1016/bs.pmbts.2014.11.010] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Pain sensing neurons in the periphery (called nociceptors) and the central neurons that receive their projections show remarkable plasticity following injury. This plasticity results in amplification of pain signaling that is now understood to be crucial for the recovery and survival of organisms following injury. These same plasticity mechanisms may drive a transition to a nonadaptive chronic pain state if they fail to resolve following the termination of the healing process. Remarkable advances have been achieved in the past two decades in understanding the molecular mechanisms that underlie pain plasticity following injury. The mechanisms bear a striking resemblance to molecular mechanisms involved in learning and memory processes in other brain regions, including the hippocampus and cerebral cortex. Here those mechanisms, their commonalities and subtle differences, will be highlighted and their role in causing chronic pain will be discussed. Arising from these data is the striking argument that chronic pain is a disease of the nervous system, which distinguishes this phenomena from acute pain that is frequently a symptom alerting the organism to injury. This argument has important implications for the development of disease modifying therapeutics.
Collapse
Affiliation(s)
- Theodore J Price
- Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas, USA.
| | - Kufreobong E Inyang
- Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| |
Collapse
|
6
|
Chen J, Huang J, Wei YY, Sun XX, Wang W, Bai L, Wang YY, Kaneko T, Li YQ, Wu SX. Birth-date dependent arrangement of spinal enkephalinergic neurons: evidence from the preproenkephalin-green fluorescent protein transgenic mice. Neuroscience 2013; 260:47-58. [PMID: 24333967 DOI: 10.1016/j.neuroscience.2013.12.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/17/2013] [Accepted: 12/05/2013] [Indexed: 12/29/2022]
Abstract
Enkephalin (ENK) has been postulated to play important roles in modulating nociceptive transmission, and it has been proved that ENKergic neurons acted as a critical component of sensory circuit in the adult spinal cord. Revealing the developmental characteristics of spinal ENKergic neurons will be helpful for understanding the formation and alteration of the sensory circuit under pain status. However, the relationship between the embryonic birth date and the adult distribution of ENKergic neurons has remained largely unknown due to the difficulties in visualizing the ENKergic neurons clearly. Taking advantage of the preproenkephalin-green fluorescent protein (PPE-GFP) transgenic mice in identifying ENKergic neurons, we performed the current birth-dating study and examined the spinal ENKergic neurogenesis. The ENKergic neurons born on different developmental stages and their final location during adulthood were investigated by combining bromodeoxyuridine (BrdU) incorporation and GFP labeling. The spinal ENKergic neurogenesis was restricted at E9.5 to E14.5, and fitted in the same pattern of spinal neurogenesis. Further comparative analysis revealed that spinal ENKergic neurons underwent heterogeneous characteristics. Our study also indicated that the laminar arrangement of ENKergic neurons in the superficial spinal dorsal horn depended on the neurogenesis stages. Taken together, the present study suggested that the birth date of ENKergic neurons is one determinant for their arrangement and function.
Collapse
Affiliation(s)
- J Chen
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - J Huang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - Y-Y Wei
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - X-X Sun
- Department of Anesthesiology, School of Stomatology, Fourth Military Medical University, Xi'an 710032, PR China
| | - W Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - L Bai
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - Y-Y Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - T Kaneko
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Y-Q Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China.
| | - S-X Wu
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, Fourth Military Medical University, Xi'an 710032, PR China.
| |
Collapse
|
7
|
Amandusson Å, Blomqvist A. Estrogenic influences in pain processing. Front Neuroendocrinol 2013; 34:329-49. [PMID: 23817054 DOI: 10.1016/j.yfrne.2013.06.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 06/19/2013] [Accepted: 06/20/2013] [Indexed: 12/24/2022]
Abstract
Gonadal hormones not only play a pivotal role in reproductive behavior and sexual differentiation, they also contribute to thermoregulation, feeding, memory, neuronal survival, and the perception of somatosensory stimuli. Numerous studies on both animals and human subjects have also demonstrated the potential effects of gonadal hormones, such as estrogens, on pain transmission. These effects most likely involve multiple neuroanatomical circuits as well as diverse neurochemical systems and they therefore need to be evaluated specifically to determine the localization and intrinsic characteristics of the neurons engaged. The aim of this review is to summarize the morphological as well as biochemical evidence in support for gonadal hormone modulation of nociceptive processing, with particular focus on estrogens and spinal cord mechanisms.
Collapse
Affiliation(s)
- Åsa Amandusson
- Department of Clinical Neurophysiology, Uppsala University, 751 85 Uppsala, Sweden.
| | | |
Collapse
|
8
|
Ma W, St-Jacques B, Cruz Duarte P. Targeting pain mediators induced by injured nerve-derived COX2 and PGE2 to treat neuropathic pain. Expert Opin Ther Targets 2012; 16:527-40. [DOI: 10.1517/14728222.2012.680955] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
9
|
Ma W. Chronic prostaglandin E2 treatment induces the synthesis of the pain-related peptide substance P and calcitonin gene-related peptide in cultured sensory ganglion explants. J Neurochem 2010; 115:363-72. [PMID: 20666934 DOI: 10.1111/j.1471-4159.2010.06927.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Prostaglandin E2 (PGE2) is a well known pain and pro-inflammatory mediator abundantly produced in inflamed tissue. It causes pain by directly exciting nociceptive primary sensory neurons (nociceptors) and indirectly stimulating the release of pain-related peptide substance P (SP) and calcitonin gene-related peptide (CGRP). In an ex vivo culture of sensory ganglion explants, we tested the hypothesis that PGE2 could induce the synthesis of SP and CGRP in nociceptors. A stabilized PGE2 analog, 16,16-dimethyl PGE2, in a concentration- and time-dependent manner, significantly increased mRNA and peptide levels of SP and CGRP. The agonists of EP1 and EP4 receptors also significantly increased SP and CGRP levels. Moreover, 16,16-dimethyl PGE2-induced SP and CGRP were blocked by EP1 and EP4 antagonists as well as the inhibitors of both protein kinase A and protein kinase C. Nerve growth factor was partially involved in PGE2-induced SP and CGRP synthesis. Taken together, these results indicate that PGE2 contributes to the synthesis of SP and CGRP in nociceptors, an event mediated by EP1 and EP4 receptors, nerve growth factor and protein kinase A and protein kinase C signalling pathways. We thus conclude that facilitating the synthesis of pain-related peptides in nociceptors is a novel mechanism underlying the role of PGE2 in nociception and chronic pain states.
Collapse
Affiliation(s)
- Weiya Ma
- Douglas Mental Health University Institute, McGill University, Montreal, Quebec, Canada.
| |
Collapse
|
10
|
Triggering genetically-expressed transneuronal tracers by peripheral axotomy reveals convergent and segregated sensory neuron-spinal cord connectivity. Neuroscience 2009; 163:1220-32. [PMID: 19647044 DOI: 10.1016/j.neuroscience.2009.07.051] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 07/21/2009] [Indexed: 11/20/2022]
Abstract
To better understand the mechanisms through which non-painful and painful stimuli evoke behavior, new resources to dissect the complex circuits engaged by subsets of primary afferent neurons are required. This is especially true to understand the consequences of injury, when reorganization of central nervous system circuits likely contributes to the persistence of pain. Here we describe a transgenic mouse line (ZWX) in which there is Cre-recombinase-dependent expression of a transneuronal tracer, wheat germ agglutinin (WGA), in primary somatic or visceral afferent neurons, but only after transection of their peripheral axons. The latter requirement allows for both regional and temporal control of tracer expression, even in the adult. Using a variety of Cre lines to target WGA transport to subpopulations of sensory neurons, here we demonstrate the extent to which myelinated and unmyelinated "pain" fibers (nociceptors) engage different spinal cord circuits. We found significant convergence (i.e., manifest as WGA-transneuronal labeling) of unmyelinated afferents, including the TRPV1-expressing subset, and myelinated afferents to NK1-receptor-expressing neurons of lamina I. By contrast, PKCgamma interneurons of inner lamina II only receive a myelinated afferent input. This differential distribution of WGA labeling in the spinal cord indicates that myelinated and unmyelinated sensory neurons target different and spatially segregated populations of postsynaptic neurons. On the other hand, we show that neurons of deeper laminae (III-V) receive direct (i.e., monosynaptic) inputs from myelinated afferents and polysynaptic input from unmyelinated afferents. Taken together, our results indicate that peripheral sensory information is transmitted to the central nervous system both through segregated and convergent pathways.
Collapse
|
11
|
Kainate receptors are primarily postsynaptic to SP-containing axon terminals in the trigeminal dorsal horn. Brain Res 2007; 1184:149-59. [PMID: 17964552 DOI: 10.1016/j.brainres.2007.09.070] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Revised: 09/25/2007] [Accepted: 09/26/2007] [Indexed: 02/05/2023]
Abstract
Kainate receptors (KARs) are involved in the modulation and transmission of nociceptive information from peripheral afferents to neurons in the spinal cord and trigeminal dorsal horns. KARs are found at both pre- and postsynaptic sites in the dorsal horn. We hypothesized that KARs and Substance P (SP), a modulatory neuropeptide that is used as a marker of nociceptive afferents, have a complex interactive relationship. To determine the cellular relationship and connectivity between KARs and SP afferents, we used electron microscopic dual immunocytochemical analysis to examine the ultrastructural localization of KAR subunits GluR5, 6 and 7 (GluR5,6,7) in relation to SP within laminae I and II in the rat trigeminal dorsal horn. KARs were distributed both postsynaptically in dendrites and somata (51% of GluR5,6,7 immunoreactive (-ir) profiles) and presynaptically in axons and axon terminals (45%). We also found GluR5,6,7-ir glial profiles (5%). The majority of SP-ir profiles were presynaptic axons and axon terminals. SP-ir dendritic profiles were rare, yet 23% contained GluR5,6,7 immunoreactivity. GluR5,6,7 and SP were also colocalized at presynaptic sites (18% of GluR5,6,7-ir axons and axon terminals contained SP; while 11% of SP-ir axons and axon terminals contained GluR5,6,7). The most common interaction between KARs and SP we observed was GluR5,6,7-ir dendrites contacted by SP-ir axon terminals; 54% of the dendritic targets of SP-ir axon terminals were GluR5,6,7-ir. These results provide anatomical evidence that KARs primarily mediate nociceptive transmission postsynaptic to SP-containing afferents and may also modulate the presynaptic release of SP and glutamate in trigeminal dorsal horn.
Collapse
|
12
|
Watanabe H, Nakayama D, Yuhki M, Sawai T, Sakurada W, Katsuyama S, Hayashi T, Watanabe C, Mizoguchi H, Fujimura T, Sakurada T, Sakurada S. Differential inhibitory effects of mu-opioids on substance P- and capsaicin-induced nociceptive behavior in mice. Peptides 2006; 27:760-8. [PMID: 16226344 DOI: 10.1016/j.peptides.2005.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Revised: 08/02/2005] [Accepted: 08/22/2005] [Indexed: 11/22/2022]
Abstract
The antinociceptive mechanisms of the selective mu-opioid receptor agonists [D-Ala2,NMePhe4,Gly(ol)5]enkephalin (DAMGO), H-Tyr-D-Arg-Phe-beta-Ala-OH (TAPA) or H-Tyr-D-Arg-Phe-beta-Ala-NH2 (TAPA-NH2) against substance P (SP)- or capsaicin-elicited nociceptive behaviors was investigated in mice. DAMGO, TAPA or TAPA-NH2 given intrathecally inhibited the nociceptive behaviors elicited by intrathecally administered SP or capsaicin, and these antinociceptive effects were completely eliminated by intrathecal co-administration with D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), a selective mu-opioid receptor antagonist. Pretreatment subcutaneously with naloxonazine, a selective mu1-opioid receptor antagonist, partially attenuated the antinociceptive effect of TAPA-NH2, but not DAMGO and TAPA, against SP. However, the antinociception induced by TAPA, but not DAMGO and TAPA-NH2, against capsaicin was significantly inhibited by naloxonazine. On the other hand, co-administration intrathecally with Tyr-D-Pro-Trp-Gly-NH2 (D-Pro2-Tyr-W-MIF-1), a selective mu2-opioid receptor antagonist, significantly attenuated the antinociceptive effects of DAMGO, but not TAPA and TAPA-NH2, against capsaicin, while the antinociceptions induced by three opioid peptides against SP were significantly inhibited by D-Pro2-Tyr-W-MIF-1. These results suggest that differential inhibitory mechanisms on pre- and postsynaptic sites in the spinal cord contribute to the antinociceptive effects of the three mu-opioid peptides.
Collapse
Affiliation(s)
- Hiroyuki Watanabe
- Department of Physiology and Anatomy, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
The endogenous opioid system is one of the most studied innate pain-relieving systems. This system consists of widely scattered neurons that produce three opioids: beta-endorphin, the met- and leu-enkephalins, and the dynorphins. These opioids act as neurotransmitters and neuromodulators at three major classes of receptors, termed mu, delta, and kappa, and produce analgesia. Like their endogenous counterparts, the opioid drugs, or opiates, act at these same receptors to produce both analgesia and undesirable side effects. This article examines some of the recent findings about the opioid system, including interactions with other neurotransmitters, the location and existence of receptor subtypes, and how this information drives the search for better analgesics. We also consider how an understanding of the opioid system affects clinical responses to opiate administration and what the future may hold for improved pain relief. The goal of this article is to assist clinicians to develop pharmacological interventions that better meet their patient's analgesic needs.
Collapse
Affiliation(s)
- Janean E Holden
- Department of Medical-Surgical Nursing, The University of Illinois at Chicago, Illinois 60612-7350, USA.
| | | | | |
Collapse
|
14
|
Kawate T, Sakamoto H, Yang C, Li Y, Shimada O, Atsumi S. Immunohistochemical study of delta and mu opioid receptors on synaptic glomeruli with substance P-positive central terminals in chicken dorsal horn. Neurosci Res 2005; 53:279-87. [PMID: 16165241 DOI: 10.1016/j.neures.2005.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Accepted: 07/14/2005] [Indexed: 11/28/2022]
Abstract
In an attempt to clarify the mechanism underlying the regulation of the release of substance P (SP) from the central axon terminals of the synaptic glomeruli in lamina II of the dorsal horn, we examined the expression patterns of delta and mu opioid receptors (DOR and MOR) in relation to those of enkephalin (ENK) and SP in the synaptic glomeruli. DOR, MOR, ENK and SP immunoreactivities in lamina II of the dorsal horn in the chicken were examined by confocal laser scanning and electron microscopies. DOR immunoreactivity was localized in both SP-positive central terminals and peripheral elements, while MOR immunoreactivity was only localized in the peripheral elements of the synaptic glomeruli. Both of the peripheral DOR- and MOR-immunoreactive elements were shown to be vesicle-containing dendrites by electron microscopy. Dual immunohistochemistry indicated that DOR, MOR and ENK immunoreactivities were located in distinct peripheral elements. On the basis of present results, the possible roles of DOR and MOR in the regulation of the release of SP from the central axon terminals in the synaptic glomeruli are discussed.
Collapse
Affiliation(s)
- Toyoko Kawate
- Department of Anatomy, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Tamaho, Yamanashi 409-3898, Japan.
| | | | | | | | | | | |
Collapse
|
15
|
Pitcher GM, Henry JL. Nociceptive response to innocuous mechanical stimulation is mediated via myelinated afferents and NK-1 receptor activation in a rat model of neuropathic pain. Exp Neurol 2004; 186:173-97. [PMID: 15026255 DOI: 10.1016/j.expneurol.2003.10.019] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2002] [Revised: 10/08/2003] [Accepted: 10/16/2003] [Indexed: 12/29/2022]
Abstract
Peripheral nerve injury in humans can produce a persistent pain state characterized by spontaneous pain and painful responses to normally innocuous stimuli (allodynia). Here we attempt to identify some of the neurophysiological and neurochemical mechanisms underlying neuropathic pain using an animal model of peripheral neuropathy induced in male Sprague-Dawley rats by placing a 2-mm polyethylene cuff around the left sciatic nerve according to the method of Mosconi and Kruger. von Frey hair testing confirmed tactile allodynia in all cuff-implanted rats before electrophysiological testing. Rats were anesthetized and spinalized for extracellular recording from single spinal wide dynamic range neurons (L(3-4)). In neuropathic rats (days 11-14 and 42-52 after cuff implantation), ongoing discharge was greater and hind paw receptive field size was expanded compared to control rats. Activation of low-threshold sensory afferents by innocuous mechanical stimulation (0.2 N for 3 s) in the hind paw receptive field evoked the typical brief excitation in control rats. However, in neuropathic rats, innocuous stimulation also induced a nociceptive-like afterdischarge that persisted 2-3 min. This afterdischarge was never observed in control rats, and, in this model, is the distinguishing feature of the spinal neural correlate of tactile allodynia. Electrical stimulation of the sciatic nerve at 4 and at 20 Hz each produced an initial discharge that was identical in control and in neuropathic rats. This stimulation also produced an afterdischarge that was similar at the two frequencies in control rats. However, in neuropathic rats, the afterdischarge produced by 20-Hz stimulation was greater than that produced by 4-Hz stimulation. Given that acutely spinalized rats were studied, only peripheral and/or spinal mechanisms can account for the data obtained; as synaptic responses from C fibers begin to fail above approximately 5-Hz stimulation [Pain 46 (1991) 327], the afterdischarge in response to 20-Hz stimulation suggests a change mainly in myelinated afferents and a predominant role of these fibers in eliciting this afterdischarge. These data are consistent with the suggestion that peripheral neuropathy induces phenotypic changes predominantly in myelinated afferents, the sensory neurons that normally respond to mechanical stimulation. The NK-1 receptor antagonist, CP-99,994 (0.5 mg/kg, i.v.), depressed the innocuous pressure-evoked afterdischarge but not the brief initial discharge of wide dynamic range neurons, and decreased the elevated ongoing rate of discharge in neuropathic rats. These results support the concept that following peripheral neuropathy, myelinated afferents may now synthesize and release substance P. A result of this is that tonic release of substance P from the central terminals of these phenotypically altered neurons would lead to ongoing excitation of NK-1-expressing nociceptive spinal neurons. In addition, these spinal neurons would also exhibit exaggerated responses to innocuous pressure stimulation. The data in this study put forth a possible neurophysiological and neurochemical basis of neuropathic pain and identify substance P and the NK-1 receptor as potential neurochemical targets for its management.
Collapse
Affiliation(s)
- Graham M Pitcher
- Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6
| | | |
Collapse
|
16
|
Abdulla FA, Moran TD, Balasubramanyan S, Smith PA. Effects and consequences of nerve injury on the electrical properties of sensory neurons. Can J Physiol Pharmacol 2003; 81:663-82. [PMID: 12897814 DOI: 10.1139/y03-064] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nociceptive pain alerts the body to potential or actual tissue damage. By contrast, neuropathic or "noninflammatory" pain, which results from injury to the nervous system, serves no useful purpose. It typically continues for years after the original injury has healed. Sciatic nerve lesions can invoke chronic neuropathic pain that is accompanied by persistent, spontaneous activity in primary afferent fibers. This activity, which reflects changes in the properties and functional expression of Na+, K+, and Ca2+ channels, initiates a further increase in the excitability of second-order sensory neurons in the dorsal horn. This change persists for many weeks. The source of origin of the pain thus moves from the peripheral to the central nervous system. We hypothesize that this centralization of pain involves the inappropriate release of peptidergic neuromodulators from primary afferent fibers. Peptides such as substance P, neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), and brain-derived neurotrophic factor (BDNF) may promote enduring changes in excitability as a consequence of neurotrophic actions on ion channel expression in the dorsal horn. Findings that form the basis of this hypothesis are reviewed. Study of the neurotrophic control of ion channel expression by spinal peptides may thus provide new insights into the etiology of neuropathic pain.
Collapse
Affiliation(s)
- Fuad A Abdulla
- Department of Physical Therapy, School of Allied Health Sciences, Hashemite University, Zarqa, Jordan
| | | | | | | |
Collapse
|
17
|
Ceccarelli I, Fiorenzani P, Massafra C, Aloisi AM. Long-term ovariectomy changes formalin-induced licking in female rats: the role of estrogens. Reprod Biol Endocrinol 2003; 1:24. [PMID: 12646052 PMCID: PMC151796 DOI: 10.1186/1477-7827-1-24] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2003] [Accepted: 02/14/2003] [Indexed: 12/02/2022] Open
Abstract
Gonadal hormones have been shown to exert modulatory effects on nociception and analgesia. To investigate the role of gonadal hormones in the response by female rats to both phasic and persistent nociceptive stimulation, we evaluated the effects of long-term ovariectomy (OVX, 6 months) on the thermal pain threshold and on formalin-induced responses. The thermal pain threshold was evaluated with the plantar test apparatus, while persistent pain was induced by a subcutaneous injection of dilute formalin (50 microliter, 10%) in the dorsal hind paw. The formalin test was carried out in an open field apparatus where the animal's spontaneous behavior and formalin-induced responses (licking duration, flinching frequency and flexing duration of the injected paw) were recorded for 60 min. Estradiol and corticosterone plasma levels were determined in blood collected from the anesthetized animals at the end of the test. In OVX females, the duration of formalin-induced licking was longer than in Intact females during both the first and the second phase; flinching and flexing did not differ from Intact. The thermal pain threshold was only slightly affected by OVX. Estradiol and corticosterone were lower in OVX females than Intact ones. These data indicate that long-term depletion of gonadal hormones in female rats modulates the pain-induced behavioral responses related to supraspinal neural circuits (licking of the injected paw) rather than more spinally mediated responses such as formalin-induced flinching and withdrawal latency in the plantar test.
Collapse
Affiliation(s)
- Ilaria Ceccarelli
- Department of Physiology, Section of Neuroscience and Applied Physiology, University of Siena, via Aldo Moro, 53100 Siena, Italy
| | - Paolo Fiorenzani
- Department of Physiology, Section of Neuroscience and Applied Physiology, University of Siena, via Aldo Moro, 53100 Siena, Italy
| | - Cosimo Massafra
- Department of Physiology, Section of Neuroscience and Applied Physiology, University of Siena, via Aldo Moro, 53100 Siena, Italy
| | - Anna Maria Aloisi
- Department of Physiology, Section of Neuroscience and Applied Physiology, University of Siena, via Aldo Moro, 53100 Siena, Italy
| |
Collapse
|
18
|
Spinal neurons that possess the substance P receptor are required for the development of central sensitization. J Neurosci 2002. [PMID: 12388616 DOI: 10.1523/jneurosci.22-20-09086.2002] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In previous studies, we have shown that loss of spinal neurons that possess the substance P receptor (SPR) attenuated pain and hyperalgesia produced by capsaicin, inflammation, and nerve injury. To determine the role of SPR-expressing neurons in modulating pain and hyperalgesia, responses of superficial and deep lumbar spinal dorsal horn neurons evoked by mechanical and heat stimuli and by capsaicin were made after ablation of SPR-expressing neurons using the selective cytotoxin conjugate substance P-saporin (SP-SAP). Morphological analysis and electrophysiological recordings were made after intrathecal infusion of vehicle, saporin alone, or SP-SAP. SP-SAP, but not vehicle or SAP alone, produced an approximately 62% decrease in SPR-expressing neurons in the dorsal horn. Loss of SPR-expressing neurons diminished the responses of remaining neurons to intraplantar injection of capsaicin. Peak responses to 10 microg of capsaicin were approximately 65% lower in animals pretreated with SP-SAP compared with controls. Additionally, sensitization to mechanical and heat stimuli that normally follows capsaicin was rarely observed. Importantly, responses to mechanical and heat stimuli in the absence of capsaicin were not altered after SP-SAP treatment. In addition, nociceptive neurons did not exhibit windup in the SP-SAP-treated group. These results demonstrate that SPR-expressing neurons located in the dorsal horn are a pivotal component of the spinal circuits involved in triggering central sensitization and hyperalgesia. It appears that this relatively small population of neurons can regulate the physiological properties of other nociceptive neurons and drive central sensitization.
Collapse
|
19
|
Smith PA, Stebbing MJ, Moran TD, Tarkkila P, Abdulla FA. Neuropathic pain and the electrophysiology and pharmacology of nerve injury. Drug Dev Res 2002. [DOI: 10.1002/ddr.10013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
20
|
Li YQ, Li JL, Li H, Kaneko T, Mizuno N. Protein kinase C gamma-like immunoreactivity of trigeminothalamic neurons in the medullary dorsal horn of the rat. Brain Res 2001; 913:159-64. [PMID: 11549380 DOI: 10.1016/s0006-8993(01)02777-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We examined protein kinase C gamma-like immunoreactivity (PKCgamma-LI) of trigeminothalamic neurons in the rat medullary dorsal horn (MDH) after injecting a retrograde tracer, Fluoro-Gold (FG), into the thalamus. Over 90% of FG-labeled neurons in the marginal layer (lamina I) and a few FG-labeled neurons in the superficial part of the magnocellular layer (lamina III) showed PKCgamma-LI. No PKCgamma-neurons in the substantia gelatinosa (lamina II) were labeled with FG. PKCgamma-mediated regulation of trigeminothalamic neurons may contribute to the changes in MDH activity during persistent pain.
Collapse
Affiliation(s)
- Y Q Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, 710032, Xi'an, PR China
| | | | | | | | | |
Collapse
|
21
|
Miao FJ, Benowitz NL, Levine JD. Endogenous opioids suppress activation of nociceptors by sub-nanomolar nicotine. Br J Pharmacol 2001; 133:23-8. [PMID: 11325790 PMCID: PMC1572752 DOI: 10.1038/sj.bjp.0704031] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2000] [Revised: 02/12/2001] [Accepted: 02/13/2001] [Indexed: 11/09/2022] Open
Abstract
1. Nicotine can activate primary afferent nociceptors, one result of which is to increase neurogenic plasma extravasation. In this study we have demonstrated a novel proinflammatory effect of sub-nanomolar nicotine, mediated by peripheral action at sensory neurons. This action is normally masked by adrenal medulla-derived delta-opioid receptor agonists. 2. While neurogenic plasma extravasation in the knee joint of the rat was not increased by intra-articular perfusion of nicotine (10(-8) M), perfusion of nicotine, at concentrations as low as 10(-10) M, combined with naloxone to block opioid receptors (or naltrindole to block delta-opioid receptors) was able to enhance bradykinin-induced plasma extravasation. This pro-inflammatory effect of intra-articular nicotine was mimicked by subcutaneous nicotine which was abolished by intra-articularly-administered hexamethonium, a nicotinic receptor antagonist. 3. Following denervation of the adrenal medulla, intra-articular nicotine, alone at 10(-8) M, enhanced plasma extravasation, which was no longer enhanced by naloxone. 4. Destruction of primary afferents by neonatal treatment with capsaicin or blockade of sensory neurotransmitter by neurokinin-1 receptor antagonist RP-87,580 abolished the pro-inflammatory effect of nicotine. 5. The effect of nicotine we describe in promoting inflammation is exerted at extremely low concentrations and therefore could have relevance to smokers, patients receiving medicinal nicotine as therapy and even second-hand smokers. Since receptor mechanisms on peripheral terminals of nociceptors may also be present on central terminals, actions of the endogenous nicotinic agonist acetylcholine, at central terminals of primary afferents or at other sites in the central nervous system, may be similarly modulated by opioids.
Collapse
Affiliation(s)
- F J Miao
- Department of Oral and Maxillofacial Surgery, University of California-San Francisco, San Francisco, CA 94143, USA.
| | | | | |
Collapse
|
22
|
Li YQ, Li H, Yang K, Wang ZM, Kaneko T, Mizuno N. Intracellular labeling study of neurons in the superficial part of the magnocellular layer of the medullary dorsal horn of the rat. J Comp Neurol 2000; 428:641-55. [PMID: 11077418 DOI: 10.1002/1096-9861(20001225)428:4<641::aid-cne5>3.0.co;2-q] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Morphology and electrical membrane properties of neurons in the superficial part of the magnocellular layer of the rat medullary dorsal horn (MDH: caudal subnucleus of the spinal trigeminal nucleus) were examined by using horizontal slice preparations. Intracellular recording and biocytin-injection combined with histochemical and immunohistochemical staining were done. Twenty-four neurons were examined successfully and classified into projection neurons (PNs) and intrinsic neurons (INs). The PNs were further divided into type I PNs (I-PNs) and type II PNs (II-PNs). The I-PNs sent axons to the medullary reticular formation; the II-PNs sent axons to the interpolar subnucleus of the spinal trigeminal nucleus but had no axons extending to the medullary reticular formation. The INs that sent no axons to the brain regions outside the MDH were also divided into small INs with spiny dendrites (INSSs) and large INs with aspiny dendrites (INLAs). The dendritic fields of the PNs extended to laminae I and II of the MDH and occasionally further to the spinal tract of the trigeminal nerve, whereas those of the INs were confined within the magnocellular layer of the MDH. The axonal branches of each IN formed a dense axonal mesh around the cell body of the parent neuron. Although the main bodies of the axonal fields of the INs were located in the magnocellular layer, some axonal branches extended to laminae I and II of the MDH. Immunoreactivity for NK1 receptor (substance P receptor) was found in approximately half of the PNs but not in the INs. Although no strong correlation was found between morphology and electrical membrane properties, there were some differences in electrical properties among the morphologically classified neuron groups, e.g., hyperpolarizing sag was observed in some PNs but not in the Ins; inward rectification was observed in some of the INSSs and INLAs but not in the PNs; the slow ramp depolarization and the slow afterdepolarization were observed in all INSSs examined but not in the PNs or INLAs.
Collapse
Affiliation(s)
- Y Q Li
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, People's Republic of China
| | | | | | | | | | | |
Collapse
|
23
|
Abstract
Substance P (SP) is a peptide that is present in unmyelinated primary afferents to the dorsal horn and is released in response to painful or noxious stimuli. Opiates active at the mu-opiate receptor (MOR) produce antinociception, in part, through modulation of responses to SP. MOR ligands may either inhibit the release of SP or reduce the excitatory responses of second-order neurons to SP. We examined potential functional sites for interactions between SP and MOR with dual electron microscopic immmunocytochemical localization of the SP receptor (NK1) and MOR in rat trigeminal dorsal horn. We also examined the relationship between SP-containing profiles and NK1-bearing profiles. We found that 56% of SP-immunoreactive terminals contact NK1 dendrites, whereas 34% of NK1-immunoreactive dendrites receive SP afferents. This result indicates that there is not a significant mismatch between sites of SP release and available NK1 receptors, although receptive neurons may contain receptors at sites distant from the peptide release site. With regard to opioid receptors, we found that many MOR-immunoreactive dendrites also contain NK1 (32%), whereas a smaller proportion of NK1-immunoreactive dendrites contain MOR (17%). Few NK1 dendrites (2%) were contacted by MOR-immunoreactive afferents. These results provide the first direct evidence that MORs are on the same neurons as NK1 receptors, suggesting that MOR ligands directly modulate SP-induced nociceptive responses primarily at postsynaptic sites, rather than through inhibition of SP release from primary afferents. This colocalization of NK1 and MORs has significant implications for the development of pain therapies targeted at these nociceptive neurons.
Collapse
|
24
|
McLeod AL, Ritchie J, Cuello AC, Julien JP, Henry JL, Ribeiro-da-Silva A. Upregulation of an opioid-mediated antinociceptive mechanism in transgenic mice over-expressing substance P in the spinal cord. Neuroscience 2000; 96:785-9. [PMID: 10727796 DOI: 10.1016/s0306-4522(99)00606-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In transgenic mice expressing ectopic substance P fibres in the spinal white matter, a normally innocuous mechanical stimulus induces hyperalgesia and allodynia which are reversed by substance P and N-methyl-D-aspartate receptor antagonists. This period of enhanced excitation is followed by a rebound overshoot in these animals. As previous evidence indicates opioid mechanisms in a similar rebound in normal animals, the present study was done to determine the effects of systemic administration of morphine and the opiate receptor antagonist, naloxone, on the stimulus-induced responses in the tail withdrawal reflex. Once baseline reaction times had been taken, different combinations of saline, naloxone and morphine were administered intraperitoneally to transgenic and control mice of either sex. A mechanical conditioning stimulus of 450g was then applied to the tip of the tail for 2s. This stimulus was innocuous in control mice given saline or naloxone, but provoked a nociceptive response in transgenic mice given these compounds. In control and transgenic mice, following morphine administration there was an antinociceptive effect. In control mice the subsequent mechanical stimulus had no effect. However, in transgenic mice the mechanical stimulus produced a further antinociception. Naloxone blocked the effect of morphine and the subsequent conditioning stimulus in both control and transgenic mice. The results indicate that while morphine is equally effective on the withdrawal reflex in both types of animal, in the transgenic mice morphine reveals an intrinsic, naloxone-sensitive antinociceptive mechanism. The data are interpreted to suggest that over-expression of substance P or some other factor in the spinal cord of transgenic mice is associated with the up-regulation or facilitation of an opiate-mediated intrinsic antinociceptive mechanism. This is a novel observation because the genetic manipulation in this transgenic mouse results in a transient over-expression of nerve growth factor during development that leads to the formation of ectopic primary afferent fibres in the spinal cord containing substance P. These fibres persist indefinitely after the nerve growth factor levels return to normal. Opioid mechanisms, which are likely of dorsal horn origin, do not fall under the direct influence of nerve growth factor mechanisms and therefore the intriguing possibility is raised that opioid mechanisms in the spinal cord are regulated at least in part by substance P-related mechanisms.
Collapse
Affiliation(s)
- A L McLeod
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Canada
| | | | | | | | | | | |
Collapse
|
25
|
Ikeda H, Asai T, Murase K. Robust changes of afferent-induced excitation in the rat spinal dorsal horn after conditioning high-frequency stimulation. J Neurophysiol 2000; 83:2412-20. [PMID: 10758142 DOI: 10.1152/jn.2000.83.4.2412] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the neuronal plasticity in the spinal dorsal horn and its relationship with spinal inhibitory networks using an optical-imaging method that detects neuronal excitation. High-intensity single-pulse stimulation of the dorsal root activating both A and C fibers evoked an optical response in the lamina II (the substantia gelatinosa) of the dorsal horn in transverse slices of 12- to 25-day-old rat spinal cords stained with a voltage-sensitive dye, RH-482. The optical response, reflecting the net neuronal excitation along the slice-depth, was depressed by 28% for more than 1 h after a high-frequency conditioning stimulation of A fibers in the dorsal root (3 tetani of 100 Hz for 1 s with an interval of 10 s). The depression was not induced in a perfusion solution containing an NMDA antagonist, DL-2-amino-5-phosphonovaleric acid (AP5; 30 microM). In a solution containing the inhibitory amino acid antagonists bicuculline (1 microM) and strychnine (3 microM), and also in a low Cl(-) solution, the excitation evoked by the single-pulse stimulation was enhanced after the high-frequency stimulation by 31 and 18%, respectively. The enhanced response after conditioning was depotentiated by a low-frequency stimulation of A fibers (0.2-1 Hz for 10 min). Furthermore, once the low-frequency stimulation was applied, the high-frequency conditioning could not potentiate the excitation. Inhibitory transmissions thus regulate the mode of synaptic plasticity in the lamina II most likely at afferent terminals. The high-frequency conditioning elicits a long-term depression (LTD) of synaptic efficacy under a greater activity of inhibitory amino acids, but it results in a long-term potentiation (LTP) when inhibition is reduced. The low-frequency preconditioning inhibits the potentiation induction and maintenance by the high-frequency conditioning. These mechanisms might underlie robust changes of nociception, such as hypersensitivity after injury or inflammation and pain relief after electrical or cutaneous stimulation.
Collapse
Affiliation(s)
- H Ikeda
- Department of Human and Artificial Intelligence Systems, Fukui University, Fukui 910, Japan
| | | | | |
Collapse
|
26
|
Aicher SA, Sharma S, Cheng PY, Liu-Chen LY, Pickel VM. Dual ultrastructural localization of mu-opiate receptors and substance p in the dorsal horn. Synapse 2000; 36:12-20. [PMID: 10700022 DOI: 10.1002/(sici)1098-2396(200004)36:1<12::aid-syn2>3.0.co;2-e] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Opiates active at the mu-opiate receptor (MOR) produce antinociception, in part, through actions involving substance P (SP), a peptide present in both unmyelinated primary afferents and interneurons within the dorsal horn. We examined potential functional sites for interactions between SP and MOR by using dual electron microscopic immunocytochemical localization of antisera against SP and a sequence-specific antipeptide antibody against MOR in rat cervical spinal dorsal horn. The distribution was compared with that of the functionally analogous dorsal horn of the trigeminal nucleus caudalis. Many of the SP-immunoreactive terminals in the dorsal horn contacted dendrites that contain MOR (53% in trigeminal; 70% in cervical spinal cord). Conversely, within the cervical spinal dorsal horn 79% of the MOR-labeled dendrites that received any afferent input were contacted by at least one SP-containing axon or terminal. Although SP-immunoreactive dendrites were rare, many of these (48%) contained MOR, suggesting that the activity of SP-containing spinal interneurons may be regulated by MOR ligands. A few SP-labeled terminals also contained MOR (12% in trigeminal; 6% in cervical spinal cord). These data support the idea that MOR ligands produce antinociception primarily through modulation of postsynaptic second-order nociceptive neurons in the dorsal horns of spinal cord and spinal trigeminal nuclei, some of which contain SP. They also suggest, however, that in each region, MOR agonists can act presynaptically to control the release of SP and/or glutamate from afferent terminals. The post- and presynaptic MOR sites are likely to account for the potency of MOR agonists as analgesics.
Collapse
Affiliation(s)
- S A Aicher
- Cornell University Medical College, Department of Neurology and Neuroscience, Division of Neurobiology, New York, New York 10021, USA.
| | | | | | | | | |
Collapse
|
27
|
Hirst EM, Johnson TC, Li Y, Raisman G. Improved post-embedding immunocytochemistry of myelinated nervous tissue for electron microscopy. J Neurosci Methods 2000; 95:151-8. [PMID: 10752486 DOI: 10.1016/s0165-0270(99)00173-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The particularly high lipid content of normal mature adult myelin sheaths, together with the light fixation protocols usually necessary to retain antigenicity, combine to make white matter nervous tissue an especially problematical subject for post-embedding immuno-electron microscopy using modern acrylic resins. Fixation and infiltration modifications to standard processing schedules for Lowicryl were found to greatly improve the embedding and therefore the resulting morphology. This in turn improved the signal to noise ratio by reducing the high non-specific backgrounds usually found in poorly infiltrated areas. Using Lowicryl HM20, we have been able to obtain satisfactory immunostaining for myelin basic protein with good retention of structural integrity in the myelin of both normal and lesioned adult cortico spinal tract.
Collapse
Affiliation(s)
- E M Hirst
- Division of Neurobiology, National Institute for Medical Research, London, UK.
| | | | | | | |
Collapse
|
28
|
|
29
|
Amandusson A, Hallbeck M, Hallbeck AL, Hermanson O, Blomqvist A. Estrogen-induced alterations of spinal cord enkephalin gene expression. Pain 1999; 83:243-8. [PMID: 10534596 DOI: 10.1016/s0304-3959(99)00109-8] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Enkephalin-synthesizing neurons in the superficial laminae of the spinal and trigeminal dorsal horn are critical components of the endogenous pain-modulatory system. We have previously demonstrated that these neurons display intracellular estrogen receptors, suggesting that estrogen can potentially influence their enkephalin expression. By using Northern blot, we now show that a bolus injection of estrogen results in a rapid increase in spinal cord enkephalin mRNA levels in ovariectomized female rats. Thus, 4 h after estrogen administration the enkephalin mRNA-expression in the lumbar spinal cord was on average 68% higher (P<0.05) than in control animals injected with vehicle only. A small increase in the amount of enkephalin mRNA was also seen after 8 h (P<0.05), whereas no difference between estrogen-injected and control animals was found after 24 h or at time periods shorter than 4 h. Taken together with the previous anatomical data, the present findings imply that estrogen has an acute effect on spinal opioid levels in areas involved in the transmission of nociceptive information.
Collapse
Affiliation(s)
- A Amandusson
- Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, University of Linköping, S-581 85, Linköping, Sweden
| | | | | | | | | |
Collapse
|
30
|
Ikeda H, Asai T, Randić M, Murase K. Robust suppression of afferent-induced excitation in the rat spinal dorsal horn after conditioning low-frequency stimulation. J Neurophysiol 1999; 82:1957-64. [PMID: 10515985 DOI: 10.1152/jn.1999.82.4.1957] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The neuronal plasticity in the spinal dorsal horn induced after conditioning low-frequency stimulation of afferent A fibers, and its relationship with spinal inhibitory networks, was investigated with an optical-imaging method that detects neuronal excitation. High-intensity single-pulse stimulation of the dorsal root activating both A and C fibers evoked an optical response in the dorsal horn in transverse slices of 12- to 25-day-old rat spinal cords stained with a voltage-sensitive dye, RH-482. The optical response, reflecting the net excitation of neuronal elements along the thickness of each slice, was suppressed after a conditioning low-frequency stimulation (0.2-1 Hz for 10 min) to A fibers in the dorsal root. The degree of suppression was largest in the lamina II of the dorsal horn (48% reduction), where the majority of C fibers terminate, and much less in the deeper dorsal horn (5% reduction in laminae III-IV). The onset of suppression was somewhat slow; after the low-frequency stimulation, the magnitude of excitation gradually decreased, reached the maximum effect 30 min after the conditioning, and remained at the suppressed level for >1 h. Suppression was not observed when the low-frequency stimulation was given during a 20-min perfusion with a solution containing an NMDA-receptor antagonist, DL-2-amino-5-phosphonovaleric acid (30 microM). A brief application of an opioid-receptor antagonist, naloxone (0.5 microM), inhibited the induction, but not the maintenance, of low-frequency stimulus-induced suppression. However, treatments with the GABA(A) receptor antagonist bicuculline (1 microM) and the glycine receptor antagonist strychnine (0.3 microM) did not affect suppression induction and maintenance. In conclusion, conditioning low-frequency stimulation to A fibers interferes with the afferent-induced excitation in the dorsal horn. The low-frequency stimulation-induced suppression is maintained by a reduction of glutamatergic excitatory transmissions in the dorsal horn, not by an enhanced inhibition. Activation of the spinal opioid-mediated system by low-frequency stimulation, but not the inhibitory amino acid-mediated system, is necessary to initiate robust suppression. The long-term depression of afferent synaptic efficacy onto excitatory interneurons likely takes the primary role in the robust suppression of neuronal excitation in the dorsal horn.
Collapse
Affiliation(s)
- H Ikeda
- Department of Human and Artificial Intelligent Systems, Fukui University, Fukui 910, Japan
| | | | | | | |
Collapse
|
31
|
McLeod AL, Krause JE, Cuello AC, Ribeiro-da-Silva A. Preferential synaptic relationships between substance P-immunoreactive boutons and neurokinin 1 receptor sites in the rat spinal cord. Proc Natl Acad Sci U S A 1998; 95:15775-80. [PMID: 9861046 PMCID: PMC28120 DOI: 10.1073/pnas.95.26.15775] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/1998] [Indexed: 01/22/2023] Open
Abstract
Substance P plays an important role in the transmission of pain-related information in the dorsal horn of the spinal cord. Recent immunocytochemical studies have shown a mismatch between the distribution of substance P and its receptor in the superficial laminae of the dorsal horn. Because such a mismatch was not observed by using classical radioligand binding studies, we decided to investigate further the issue of the relationship between substance P and its receptor by using an antibody raised against a portion of the carboxyl terminal of the neurokinin 1 receptor and a bispecific monoclonal antibodies against substance P and horseradish peroxidase. Light microscopy revealed a good correlation between the distributions of substance P and the neurokinin 1 receptor, both being localized with highest densities in lamina I and outer lamina II of the spinal dorsal horn. An ultrastructural double-labeling study, combining preembedding immunogold with enzyme-based immunocytochemistry, showed that most neurokinin 1 receptor immunoreactive dendrites were apposed by substance P containing boutons. A detailed quantitative analysis revealed that neurokinin 1 receptor immunoreactive dendrites received more appositions and synapses from substance P immunoreactive terminals than those not expressing the neurokinin 1 receptor. Such preferential innervation by substance P occurred in all superficial dorsal horn laminae even though neurokinin 1 receptor immunoreactive dendrites were a minority of the total number of dendritic profiles in the above laminae. These results suggest that, contrary to the belief that neuropeptides act in a diffuse manner at a considerable distance from their sites of release, substance P should act on profiles expressing the neurokinin 1 receptor at a short distance from its site of release.
Collapse
Affiliation(s)
- A L McLeod
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | | | | | | |
Collapse
|
32
|
Goadsby PJ, Hoskin KL, Knight YE. Substance P blockade with the potent and centrally acting antagonist GR205171 does not effect central trigeminal activity with superior sagittal sinus stimulation. Neuroscience 1998; 86:337-43. [PMID: 9692766 DOI: 10.1016/s0306-4522(98)00013-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The development and use of serotonin-1B/1D agonists to treat the acute attack of migraine has been a significant advance, but their vasoconstrictor effects have lead to a search for non-vasoconstrictor approaches to the management of the acute attack of migraine. One such suggested approach has been substance P (neurokinin-1) antagonists, since substance P is involved in mediating neurogenic plasma protein extravasation and has long been held to have a role in pain transmission. In this study, one such candidate compound, GR205171, a highly lipophilic potent neurokinin-1 antagonist, has been tested in a model of trigeminovascular nociception with considerable predictive value for anti-migraine activity. The superior sagittal sinus was isolated in the alpha-chloralose (60 mg/kg, i.p., and 20 mg/kg, i.v., supplemented every 2 h)-anaesthetized cat. The sinus was stimulated electrically (100 V, 250 micros duration, 0.3 Hz) and neurons in the dorsal C2 spinal cord monitored using electrophysiological methods. In separate experiments, the animals were prepared for stimulation and then maintained for 24 h before stimulation and perfusion for Fos immunohistochemistry. Stimulation of the superior sagittal sinus resulted in activation of cells in the dorsal horn of C2. Cells fired with a probability of 0.7 +/- 0.1 at a latency of 10.7 +/- 0.2 ms. Administration of GR205171 (100 microg/kg, i.v.) had no effect on probability of firing or latency. Stimulation of the sinus in separate cats resulted in increased expression over control levels in the superficial laminae of the trigeminal nucleus caudalis and C1/2 dorsal horns. GR205171 in the same dose had no effect upon Fos expression. Inhibition of substance P by the potent, selective and brain penetrant neurokinin-1 antagonist GR205171 had no effect upon either cell firing or Fos expression in the central trigeminal cells activated by stimulation of the superior sagittal sinus. These data and the published clinical data for other compounds suggest that neurokinin-1 blockade alone will not be an effective anti-migraine strategy. Further data will be required to assess whether neurokinin-1 antagonists will have any more general value in pain.
Collapse
Affiliation(s)
- P J Goadsby
- Institute of Neurology, The National Hospital for Neurology and Neurosurgery, London, UK
| | | | | |
Collapse
|
33
|
Oxytocin modulates glutamatergic synaptic transmission between cultured neonatal spinal cord dorsal horn neurons. J Neurosci 1998. [PMID: 9502799 DOI: 10.1523/jneurosci.18-07-02377.1998] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The functional characteristics of binding sites for the neuropeptide oxytocin (OT) detected by radioautography in laminae I and II of the dorsal horn (DH) and on cultured neonatal DH neurons were studied on the latter using perforated patch-clamp recordings. The neurons were identified by their spike discharge properties and on the basis of the presence of met-enkephalin-like and glutamate decarboxylase-like immunoreactivities. OT (100 nM) never induced any membrane current at a holding potential of -60 mV but increased the frequency of spontaneously occurring AMPA receptor-mediated EPSCs or the mean amplitude of electrically evoked EPSCs in a subset (35%) of neurons. The frequency of miniature EPSCs (m-EPSCs) recorded in the presence of 0.5 microM tetrodotoxin was also increased by OT (100 nM) without any change in their mean amplitude, indicating an action at a site close to the presynaptic terminal. The decay kinetics of any type of EPSC were never modified by OT. The effect of OT was reproduced by [Thr4, Gly7]-OT (100 nM), a selective OT receptor agonist, and blocked by d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH29]-ornithine vasotocin (100 nM), a specific OT receptor antagonist. Reducing the extracellular Ca2+ concentration from 2.5 to 0.3 mM in the presence of Cd2+ (100 microM) reversibly blocked the effect of OT on m-EPSCs. The OT receptors described here may represent the substrate for modulatory actions of descending hypothalamo-spinal OT-containing pathways on the nociceptive system.
Collapse
|
34
|
Jo YH, Stoeckel ME, Schlichter R. Electrophysiological properties of cultured neonatal rat dorsal horn neurons containing GABA and met-enkephalin-like immunoreactivity. J Neurophysiol 1998; 79:1583-6. [PMID: 9497435 DOI: 10.1152/jn.1998.79.3.1583] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We have developed a culture of neurons dissociated from the most superficial laminae of the neonatal rat spinal cord dorsal horn (DH). By using the perforated patch-clamp technique, we distinguished four types of neurons based on their firing properties in response to intracellular injection of 900 ms lasting current pulses. Type 1 neurons were characterized by a tonic firing. Type 2 neurons displayed marked spike accommodation and fired brief (<500 ms) bursts of action potentials, whereas type 3 neurons fired a single spike. Type 4 neurons exhibited different types of firing patterns, but all of them possessed a time-dependent inwardly rectifying current activated by membrane hyperpolarization. Met-enkephalin-like immunoreactivity (met-ENK-LI) and glutamic acid decarboxylase-like immunoreactivity (GAD-LI) were colocalized in 42% of the neurons (n = 59), which were previously identified electrophysiologically. Type 1-4 neurons represented respectively 4, 64, 20, and 12% of the population of neurons colocalizing met-ENK-LI and GAD-LI. We conclude that the electrophysiological properties of DH neurons present in our cultures are similar to those described in acute slice or hemisected spinal cord preparations and that met-ENK-LI and GABA-LI are preferentially colocalized in type 2 neurons.
Collapse
Affiliation(s)
- Y H Jo
- Laboratoire Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519 Centre National de la Recherche Scientifique, Université Louis Pasteur, 67084 Strasbourg Cedex, France
| | | | | |
Collapse
|
35
|
Zhang X, Bao L, Arvidsson U, Elde R, Hökfelt T. Localization and regulation of the delta-opioid receptor in dorsal root ganglia and spinal cord of the rat and monkey: evidence for association with the membrane of large dense-core vesicles. Neuroscience 1998; 82:1225-42. [PMID: 9466442 DOI: 10.1016/s0306-4522(97)00341-2] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Using immunohistochemistry and immunoelectron microscopy, the localization and regulation of delta-opioid receptor-like immunoreactivity were studied in dorsal root ganglia and spinal cord of normal rat and monkey, and after peripheral axotomy. Delta-opioid receptor-like immunoreactivity was observed in many small dorsal root ganglion neurons, and in the rat most of them contained substance P and calcitonin gene-related peptide. At the ultrastructural level, delta-opioid receptor-like immunoreactivity was localized in the Golgi complex, on the membrane of the large dense-core vesicles and on the membrane of and/or inside a type of large vesicle with an interior of low electron density. The latter vesicles were often in contact with multivesicular bodies. In the superficial dorsal horn of the spinal cord, most delta-opioid receptor-positive nerve fibers contain substance P and/or calcitonin gene-related peptide, both in rat and monkey. Also, in these nerve endings delta-opioid receptor-like immunoreactivity was found on the membrane of large dense-core vesicles and on the membrane of, or in, the lucent vesicles. Occasionally, delta-opioid receptor-like immunoreactivity was observed on the plasmalemma of the terminals, particularly when the vesicles were in exocytotic contact with the plasmalemma. Peripheral axotomy induced a decrease in delta-opioid receptor-like immunoreactivity both in cell bodies in the dorsal root ganglia and in terminals in the dorsal horn. These data suggest that the delta-opioid receptor may be a constituent of the membrane of large dense-core vesicles storing and releasing neuropeptides. It is suggested that upon exocytotic release of substance P and calcitonin gene-related peptide from large dense-core vesicles, there is a transient modification of the surface of the primary afferent terminals which leads to exposure of the receptor protein so that enkephalin released from adjacent terminals can activate the receptor. The decrease in delta-opioid receptors after axotomy indicates that delta-opioid receptor-mediated inhibitory effects are attenuated at the spinal level both in the rat and monkey.
Collapse
Affiliation(s)
- X Zhang
- Department of Neuroscience, Karolinska Institute, Stockholm, Sweden
| | | | | | | | | |
Collapse
|
36
|
Abstract
Evidence is presented that the recently discovered endogenous mu-selective agonist, endomorphin-2, is localized in primary sensory afferents. Endomorphin-2-like immunoreactivity was found to be colocalized in a subset of substance P- and mu opiate receptor-containing fibers in the superficial laminae of the spinal cord and spinal trigeminal nucleus. Disruption of primary sensory afferents by mechanical (deafferentation by dorsal rhizotomy) or chemical (exposure to the primary afferent neurotoxin, capsaicin) methods virtually abolished endomorphin-2-like immunoreactivity in the dorsal horn. These results indicate that endomorphin-2 is present in primary afferent fibers where it can serve as the endogenous ligand for pre- and postsynaptic mu receptors and as a major modulator of pain perception.
Collapse
Affiliation(s)
- S Martin-Schild
- Neuroscience Training Program, Tulane University, New Orleans, LA, USA
| | | | | | | |
Collapse
|