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Anesthesiology Jan 2002Intrathecal adenosine produces a remarkably prolonged effect to relieve mechanical hypersensitivity after peripheral nerve injury in animals. The purpose of the current...
BACKGROUND
Intrathecal adenosine produces a remarkably prolonged effect to relieve mechanical hypersensitivity after peripheral nerve injury in animals. The purpose of the current study was to investigate whether this reflected an alteration in kinetics of adenosine in cerebrospinal fluid or in the number of spinal A1 adenosine receptors after nerve injury.
METHODS
Male rats were anesthetized, and the left L5 and L6 spinal nerves were ligated. Two weeks later, a lumbar intrathecal catheter and intrathecal space microdialysis catheter were inserted. Adenosine, 20 microg, was injected intrathecally in these and in normal rats, and microdialysates of the intrathecal space were obtained. Radioligand binding studies of adenosine A1 receptors were determined in spinal cord tissue from other normal and spinal nerve-ligated rats.
RESULTS
Adenosine disappeared from rat cerebrospinal fluid within 30 min after intrathecal injection, with no difference between normal and spinal nerve-ligated animals. A1 adenosine receptor binding sites in the spinal cord were increased after spinal nerve ligation. This increase disappeared when adenosine deaminase was added to the membrane homogenates, suggestive of decreased endogenous adenosine in the membranes of nerve-ligated animals.
CONCLUSION
These data show that prolonged alleviation of hypersensitivity observed with intrathecal adenosine in this animal model of neuropathic pain is not due to prolonged residence in cerebrospinal fluid, although pharmacokinetics in tissues are unknown. Similarly, there is no evidence for up-regulation in spinal A1 adenosine receptors after spinal nerve ligation, and the adenosine deaminase experiment is consistent with a depletion of adenosine in spinal cord tissue after spinal nerve ligation.
Topics: Adenosine; Analgesics; Animals; Injections, Spinal; Ligation; Male; Microdialysis; Pain; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P1; Spinal Nerves; Xanthines
PubMed: 11753009
DOI: 10.1097/00000542-200201000-00022 -
Journal of Anatomy Sep 2016In classic anatomic atlases, the spinal cord is standardly represented in its anatomical form with symmetrically emerging anterior and posterior roots, which at the...
In classic anatomic atlases, the spinal cord is standardly represented in its anatomical form with symmetrically emerging anterior and posterior roots, which at the level of the intervertebral foramen combine into the spinal nerves. The parts of the cord delimited by the boundaries of the roots are called segments or myelomeres. Associated with their regular repetitive appearance is the notion that the cord is segmentally organized. This segmental view is reinforced by clinical practice. Spinal cord roots innervate specific body parts. The level of cord trauma is diagnosed by the de-innervation symptoms of these parts. However, systemically, the case for a segmentally organized cord is not so clear. To date, developmental and genetic research points to a regionally rather than a segmentally organized cord. In the present study, to what degree the fila radicularia are segmentally implanted along the cord was investigated. The research hypothesis was that if the fila radicularia were non-segmentally implanted at the cord surface, it would be unlikely that the internal neuron stratum would be segmented. The visual segmented aspect of the myelomeres would then be the consequence of the necessary bundling of axons towards the vertebral foramen as the only exits of the vertebral canal, rather than of an underlying segment organization of the cord itself. To investigate the research hypothesis, the fila radicularia in the cervical-upper thoracic part of five spinal cords were detached from their spinal nerves and dissected in detail. The principal research question was if the fila radicularia are separated from their spinal nerves and dissected from their connective tissues up to the cord, would it be possible to reconstruct the original spinal segments from the morphology and interspaces of the fila? The dissections revealed that the anterior fila radicularia emerge from the cord at regular regionally modulated interspaces without systematic segmental delineations. The posterior fila radicularia are somewhat more segmentally implanted, but the pattern is individually inconsistent. The posterior and anterior roots have notable morphological differences, and hypotheses are presented to help explain these. The macroscopic observations are consistent with a regionally but not a segmentally organized cord. This conclusion was visually summarized in photographs of spinal cords with ipsilateral intact roots and contralateral individually dissected fila radicularia. It was suggested that this dual view of the spinal cord be added to the standard anatomic textbooks to counterbalance the current possibly biased view of a segmented cord.
Topics: Cadaver; Cervical Vertebrae; Humans; Spinal Cord; Spinal Nerve Roots; Thoracic Vertebrae
PubMed: 27173936
DOI: 10.1111/joa.12493 -
British Journal of Pharmacology Apr 20011. Adenosine (ADO) receptor activation modulates sensory transmission in the dorsal horn. Little is known about the circumstances underlying release of the purine. The...
1. Adenosine (ADO) receptor activation modulates sensory transmission in the dorsal horn. Little is known about the circumstances underlying release of the purine. The present study was conducted to investigate the effect of a novel and potent non-nucleoside adenosine kinase (AK) inhibitor, ABT-702, on the responses of dorsal horn neurones to selected peripheral stimuli. ABT-702 is orally effective to reduce behavioural signs of nociception in models of acute, inflammatory, and neuropathic pain. 2. Electrophysiological recordings were made from wide dynamic range (WDR) neurones in halothane-anaesthetized rats. ABT-702 was given subcutaneously following either carrageenan inflammation or peripheral nerve injury (L5/L6 spinal nerve ligation). Comparisons were made between carrageenan and uninjected control animals, and similarly between spinal nerve ligated (SNL) and sham operated animals. 3. ABT-702 produced inhibition of the postdischarge, wind-up and C-fibre evoked responses in both carrageenan and nerve-injured animals. Furthermore, the mechanical and thermal evoked responses were similarly reduced in SNL rats. Overall, ABT-702 produced a significantly greater inhibition of these responses in SNL rats as compared to sham controls. Similarly ABT-702 tended to produce greater effects after carrageenan inflammation, however this did not reach significance. 4. Protection of endogenous adenosine by ABT-702 therefore produces a marked inhibition of the noxious evoked neuronal activity in inflamed and neuropathic rats. Our results demonstrate a plasticity in the endogenous adenosine-mediated inhibitory system following SNL and provide a possible basis for the use of this compound for the treatment of neuropathic and other persistent pain states.
Topics: Adenosine Kinase; Animals; Behavior, Animal; Carrageenan; Dose-Response Relationship, Drug; Electrophysiology; Enzyme Inhibitors; Hot Temperature; Inflammation; Ligation; Male; Morpholines; Neurons; Pain; Peripheral Nerve Injuries; Peripheral Nerves; Posterior Horn Cells; Pyrimidines; Rats; Rats, Sprague-Dawley; Spinal Cord; Spinal Nerves
PubMed: 11264257
DOI: 10.1038/sj.bjp.0703972 -
Molecular Pain 2016Peripheral nerve injury leads to changes in gene expression in primary sensory neurons of the injured dorsal root ganglia. These changes are believed to be involved in...
BACKGROUND
Peripheral nerve injury leads to changes in gene expression in primary sensory neurons of the injured dorsal root ganglia. These changes are believed to be involved in neuropathic pain genesis. Previously, these changes have been identified using gene microarrays or next generation RNA sequencing with poly-A tail selection, but these approaches cannot provide a more thorough analysis of gene expression alterations after nerve injury.
METHODS
The present study chose to eliminate mRNA poly-A tail selection and perform strand-specific next generation RNA sequencing to analyze whole transcriptomes in the injured dorsal root ganglia following spinal nerve ligation. Quantitative real-time reverse transcriptase polymerase chain reaction assay was carried out to verify the changes of some differentially expressed RNAs in the injured dorsal root ganglia after spinal nerve ligation.
RESULTS
Our results showed that more than 50 million (M) paired mapped sequences with strand information were yielded in each group (51.87 M-56.12 M in sham vs. 51.08 M-57.99 M in spinal nerve ligation). Six days after spinal nerve ligation, expression levels of 11,163 out of a total of 27,463 identified genes in the injured dorsal root ganglia significantly changed, of which 52.14% were upregulated and 47.86% downregulated. The largest transcriptional changes were observed in protein-coding genes (91.5%) followed by noncoding RNAs. Within 944 differentially expressed noncoding RNAs, the most significant changes were seen in long interspersed noncoding RNAs followed by antisense RNAs, processed transcripts, and pseudogenes. We observed a notable proportion of reads aligning to intronic regions in both groups (44.0% in sham vs. 49.6% in spinal nerve ligation). Using quantitative real-time polymerase chain reaction, we confirmed consistent differential expression of selected genes including Kcna2, Oprm1 as well as lncRNAs Gm21781 and 4732491K20Rik following spinal nerve ligation.
CONCLUSION
Our findings suggest that next generation RNA sequencing can be used as a promising approach to analyze the changes of whole transcriptomes in dorsal root ganglia following nerve injury and to possibly identify new targets for prevention and treatment of neuropathic pain.
Topics: Alternative Splicing; Animals; Ganglia, Spinal; Gene Expression Profiling; Genome; Hyperalgesia; Ligation; Lumbar Vertebrae; Male; Mice, Inbred C57BL; Peripheral Nerve Injuries; Real-Time Polymerase Chain Reaction; Reproducibility of Results; Sequence Analysis, RNA; Signal Transduction; Spinal Nerves
PubMed: 27030721
DOI: 10.1177/1744806916629048 -
European Journal of Pain (London,... Jan 2019The term 'irritable nociceptor' was coined to describe neuropathic patients characterized by evoked hypersensitivity and preservation of primary afferent fibres....
BACKGROUND
The term 'irritable nociceptor' was coined to describe neuropathic patients characterized by evoked hypersensitivity and preservation of primary afferent fibres. Oxcarbazepine is largely ineffectual in an overall patient population, but has clear efficacy in a subgroup with the irritable nociceptor profile. We examine whether neuropathy in rats induced by spinal nerve injury shares overlapping pharmacological sensitivity with the irritable nociceptor phenotype using drugs that target sodium channels.
METHODS
In vivo electrophysiology was performed in anaesthetized spinal nerve ligated (SNL) and sham-operated rats to record from wide dynamic range (WDR) neurones in the ventral posterolateral thalamus (VPL) and dorsal horn.
RESULTS
In neuropathic rats, spontaneous activity in the VPL was substantially attenuated by spinal lidocaine, an effect that was absent in sham rats. The former measure was in part dependent on ongoing peripheral activity as intraplantar lidocaine also reduced aberrant spontaneous thalamic firing. Systemic oxcarbazepine had no effect on wind-up of dorsal horn neurones in sham and SNL rats. However, in SNL rats, oxcarbazepine markedly inhibited punctate mechanical-, dynamic brush- and cold-evoked neuronal responses in the VPL and dorsal horn, with minimal effects on heat-evoked responses. In addition, oxcarbazepine inhibited spontaneous activity in the VPL. Intraplantar injection of the active metabolite licarbazepine replicated the effects of systemic oxcarbazepine, supporting a peripheral locus of action.
CONCLUSIONS
We provide evidence that ongoing activity in primary afferent fibres drives spontaneous thalamic firing after spinal nerve injury and that oxcarbazepine through a peripheral mechanism exhibits modality-selective inhibitory effects on sensory neuronal processing.
SIGNIFICANCE
The inhibitory effects of lidocaine and oxcarbazepine in this rat model of neuropathy resemble the clinical observations in the irritable nociceptor patient subgroup and support a mechanism-based rationale for bench-to-bedside translation when screening novel drugs.
Topics: Action Potentials; Animals; Ligation; Male; Neuralgia; Neurons; Nociceptors; Oxcarbazepine; Peripheral Nervous System Diseases; Phenotype; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Spinal Nerves; Thalamus; Ventral Thalamic Nuclei; Voltage-Gated Sodium Channel Blockers
PubMed: 30091265
DOI: 10.1002/ejp.1300 -
Molecular Pain Jan 2014The past decade has seen an abundance of transcriptional profiling studies of preclinical models of persistent pain, predominantly employing microarray technology. In... (Comparative Study)
Comparative Study
BACKGROUND
The past decade has seen an abundance of transcriptional profiling studies of preclinical models of persistent pain, predominantly employing microarray technology. In this study we directly compare exon microarrays to RNA-seq and investigate the ability of both platforms to detect differentially expressed genes following nerve injury using the L5 spinal nerve transection model of neuropathic pain. We also investigate the effects of increasing RNA-seq sequencing depth. Finally we take advantage of the "agnostic" approach of RNA-seq to discover areas of expression outside of annotated exons that show marked changes in expression following nerve injury.
RESULTS
RNA-seq and microarrays largely agree in terms of the genes called as differentially expressed. However, RNA-seq is able to interrogate a much larger proportion of the genome. It can also detect a greater number of differentially expressed genes than microarrays, across a wider range of fold changes and is able to assign a larger range of expression values to the genes it measures. The number of differentially expressed genes detected increases with sequencing depth. RNA-seq also allows the discovery of a number of genes displaying unusual and interesting patterns of non-exonic expression following nerve injury, an effect that cannot be detected using microarrays.
CONCLUSION
We recommend the use of RNA-seq for future high-throughput transcriptomic experiments in pain studies. RNA-seq allowed the identification of a larger number of putative candidate pain genes than microarrays and can also detect a wider range of expression values in a neuropathic pain model. In addition, RNA-seq can interrogate the whole genome regardless of prior annotations, being able to detect transcription from areas of the genome not currently annotated as exons. Some of these areas are differentially expressed following nerve injury, and may represent novel genes or isoforms. We also recommend the use of a high sequencing depth in order to detect differential expression for genes with low levels of expression.
Topics: Animals; Chromosome Mapping; Disease Models, Animal; Ganglia, Spinal; Gene Expression Profiling; Gene Expression Regulation; Genome; Male; Microarray Analysis; Neuralgia; Oligonucleotide Array Sequence Analysis; Rats; Rats, Wistar; Sensory Receptor Cells; Sequence Analysis, RNA; Spinal Cord; Spinal Nerves; Transcription, Genetic
PubMed: 24472155
DOI: 10.1186/1744-8069-10-7 -
BMC Anesthesiology Oct 2015Neuropathic pain is evasive to treat once developed, however evidence suggests that local administration of anesthetics near the time of injury reduces the development...
BACKGROUND
Neuropathic pain is evasive to treat once developed, however evidence suggests that local administration of anesthetics near the time of injury reduces the development of neuropathic pain. As abnormal electrical signaling in the damaged nerve contributes to the initiation and maintenance of neuropathic pain, local administration of anesthetics prior to injury may reduce its development. We hypothesized that local treatment with bupivacaine prior to nerve injury in a rat model of spinal nerve ligation (SNL) would attenuate the initiation and/or maintenance of neuropathic pain behaviors.
METHODS
On the day prior to SNL, baseline measures of pre-injury mechanical, thermal, and/or cold sensitivity were recorded in adult male Sprague-Dawley rats. Immediately prior to SNL or sham treatment, the right L5 nerve was perineurally bathed in either 0.05 mL bupivacaine (0.5 %) or sterile saline (0.9 %) for 30 min. Mechanical allodynia, thermal hyperalgesia, and/or cold allodynia were then examined at 3, 7, 10, 14 and 21 days following SNL.
RESULTS
Rats exhibited both mechanical and cold allodynia, but not thermal hyperalgesia, within 3 days and up to 21 days post-SNL. No significant pain behaviors were observed in sham controls. Preemptive local bupivacaine significantly attenuated both mechanical and cold allodynia as early as 10 days following SNL compared to saline controls and were not significantly different from sham controls.
CONCLUSIONS
These data indicate that local treatment with bupivacaine prior to surgical manipulations that are known to cause nerve damage may protect against the maintenance of chronic neuropathic pain.
Topics: Anesthetics, Local; Animals; Bupivacaine; Cold Temperature; Hyperalgesia; Ligation; Male; Rats; Rats, Sprague-Dawley; Spinal Nerves
PubMed: 26444970
DOI: 10.1186/s12871-015-0113-x -
The Journal of Neuroscience : the... May 2003The possible involvement of p38 mitogen-activated protein kinase activation in spinal cord and dorsal root ganglion (DRG) cells in the development of peripheral...
p38 mitogen-activated protein kinase is activated after a spinal nerve ligation in spinal cord microglia and dorsal root ganglion neurons and contributes to the generation of neuropathic pain.
The possible involvement of p38 mitogen-activated protein kinase activation in spinal cord and dorsal root ganglion (DRG) cells in the development of peripheral neuropathic pain has been explored. Ligation of the L5 spinal nerve (SNL) on one side in adult rats produces an early onset and long-lasting mechanical allodynia. This lesion results in activation of p38 in the L5 segment of the spinal cord, most prominently in the ipsilateral dorsal horn, starting soon after the lesion (<1 d) and persisting for >3 weeks. The activated p38 in the spinal cord is restricted entirely to microglia; phospho-p38 colocalizes only with the microglial marker OX-42 and not with either the neuronal marker neuronal-specific nuclear protein or the astrocyte marker GFAP. In contrast, SNL induces a delayed (>3 d) activation of p38 in the L5 DRG that occurs predominantly in neurons. Continuous injection of the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)-1H-imidazole (SB203580) via the intrathecal route, starting before the SNL surgery, reduces SNL-induced mechanical allodynia from day 1 to day 10, with maximal effects at early time points. Post-treatment with SB203580 starting on day 1 or on day 10 after surgery also reduces established mechanical allodynia. Because the reduction in neuropathic pain by p38 inhibition occurs before the appearance of p38 activation in DRG neurons, p38 activation in spinal cord microglia is likely to have a substantial role in the earliest phase of neuropathic pain. Coactivation of p38 in DRG neurons and spinal microglia may contribute to later phases of neuropathic pain.
Topics: Animals; Behavior, Animal; Enzyme Activation; Enzyme Inhibitors; Ganglia, Spinal; Hyperalgesia; Imidazoles; Injections, Spinal; Ligation; Male; Microglia; Mitogen-Activated Protein Kinases; Pain; Pain Measurement; Pyridines; Rats; Rats, Sprague-Dawley; Spinal Cord; Spinal Nerves; p38 Mitogen-Activated Protein Kinases
PubMed: 12764087
DOI: 10.1523/JNEUROSCI.23-10-04017.2003 -
Neurology Apr 2015To investigate whether the human sciatic nerve might have a consistent somatotopic organization according to proximal fascicle input by spinal nerves.
OBJECTIVES
To investigate whether the human sciatic nerve might have a consistent somatotopic organization according to proximal fascicle input by spinal nerves.
METHODS
Twelve patients (55.3 ± 15.5 years) with confirmed lesions of either the L5 or S1 spinal nerve root underwent magnetic resonance neurography of sciatic nerve fascicles including thigh and knee levels (T2-weighted sequence with fat saturation, repetition time/echo time 7,552/52 milliseconds, voxel size 0.27 × 0.27 × 3.0 mm(3)). Twenty healthy subjects and 12 additional patients with an established diagnosis of peripheral polyneuropathy served as 2 separate age- and sex-matched control groups. Two blinded readers assessed patients and controls for presence of distinct lesion patterns. Spatial maps of normalized T2 signal were rendered after segmentation and coregistration of sciatic nerve voxels to detect fascicle lesion patterns.
RESULTS
A clear somatotopic distribution of nerve fascicles was observed on cross-sections along the entire course of the sciatic nerve and was distinct between patients with L5 and those with S1 lesions. Fascicles emerging from L5 were ordered in anterolateral positions within sciatic nerve cross-sections, while fascicles emerging from S1 appeared posteromedially. Visual assessment discriminated these somatotopic lesions in all cases from both healthy and polyneuropathy controls.
CONCLUSION
A distinct pattern of somatotopy was identified within the sciatic nerve according to proximal fascicle input by L5 and S1 spinal nerves. Knowledge of human nerve somatotopy may have clinically useful implications in imaging-aided diagnosis of neuropathies.
Topics: Adult; Aged; Female; Humans; Lumbar Vertebrae; Magnetic Resonance Imaging; Male; Middle Aged; Polyneuropathies; Radiculopathy; Sacrum; Sciatic Nerve; Spinal Nerves
PubMed: 25841030
DOI: 10.1212/WNL.0000000000001526 -
Brazilian Journal of Anesthesiology... 2016The manufacture of minimally traumatic needles and synthesis of pharmacological adjuncts with safe and effective action on inhibitory and neuromodulatory synapses...
BACKGROUND AND OBJECTIVES
The manufacture of minimally traumatic needles and synthesis of pharmacological adjuncts with safe and effective action on inhibitory and neuromodulatory synapses distributed along the nociceptive pathways were crucial for a new expansion phase of spinal anesthesia. The objectives of this paper are present our clinical experience with 1330 lumbar spinal anesthesia performed with purposeful nociceptive blockade of the thoracic and cervical spinal nerves corresponding to dermatomes C4 or C3; warn about the method pathophysiological risks, and emphasize preventive standards for the safe application of the technique.
CONTENT
Review of the historical background and anatomical spinal anesthesia with cervical levels of analgesia. Description of the technique used in our institution; population anesthetized; and surgery performed with the described method. Critical exposition of the physiological, pathophysiological, and clinical effects occurred and registered during anesthesia-surgery and postoperative period.
CONCLUSION
Spinal anesthesia with nociceptive blockade to dermatome C4, or C3, is an effective option for surgery on somatic structures distal to the metamer of the third cervical spinal nerve, lasting no more than four or five hours. The method safety depends on the unrestricted respect for the essential rules of proper anesthesia.
Topics: Adolescent; Adult; Aged; Anesthesia, Spinal; Anesthetics, Local; Cervical Plexus; Female; Humans; Lumbar Vertebrae; Male; Middle Aged; Nerve Block; Retrospective Studies; Thoracic Nerves; Young Adult
PubMed: 26768937
DOI: 10.1016/j.bjane.2014.05.016