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Bartley EJ, Rhudy JL. The influence of pain catastrophizing on experimentally induced emotion and emotional modulation of nociception. THE JOURNAL OF PAIN 2008; 9:388-96. [PMID: 18226969 DOI: 10.1016/j.jpain.2007.11.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Revised: 11/14/2007] [Accepted: 11/24/2007] [Indexed: 11/17/2022]
Abstract
UNLABELLED Pain catastrophizing is associated with enhanced pain and pain-related outcomes. Unfortunately, the mechanisms underlying the catastrophizing-pain relationship are poorly understood. Given evidence suggesting significant relationships among catastrophizing, emotion, and pain, it is possible that catastrophizing may alter nociception and pain through affective processes. Research has shown that emotionally charged pictures (erotica, neutral, threat/attack scenes) manipulate emotional valence (positive affect vs negative affect) and modulate physiological and subjective nociceptive reactions (pleasure-induced inhibition, displeasure-induced facilitation). Using this methodology, the present study addressed 2 questions: (1) Does pain catastrophizing moderate affective reactions to standard emotional stimuli (eg, augmented negative affect)? and (2) Does pain catastrophizing moderate the relationship between emotion and nociception (eg, augmented displeasure-induced facilitation)? Erotic, neutral, and attack pictures were presented to 53 participants who rated their emotional responses. During pictures, noxious electric stimulations were delivered to evoke nociceptive reactions (nociceptive flexion reflex, skin conductance response, heart rate acceleration, subjective pain). Results suggest that pain catastrophizing did not moderate emotional reactions to standardized picture stimuli, nor did catastrophizing moderate the influence of emotion on nociceptive reactions. This suggests that catastrophizing does not influence pain indirectly through emotional processes. PERSPECTIVE Pain catastrophizing is commonly associated with negative emotions and maladaptive responses to pain. The current study provides evidence indicating catastrophizing does not alter pain and nociception indirectly via emotional processes.
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Affiliation(s)
- Emily J Bartley
- Department of Psychology, The University of Tulsa, Tulsa, Oklahoma 74104, USA
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352
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Baguley IJ. The excitatory:inhibitory ratio model (EIR model): An integrative explanation of acute autonomic overactivity syndromes. Med Hypotheses 2008; 70:26-35. [PMID: 17583440 DOI: 10.1016/j.mehy.2007.04.037] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 04/25/2007] [Indexed: 12/21/2022]
Abstract
Numerous medical conditions present with acute and severe autonomic and muscular overactivity. These syndromes include Neuroleptic Malignant Syndrome, Serotonin Syndrome, Dysautonomia (or paroxysmal sympathetic storms) following acquired brain injury, Autonomic Dysreflexia, Parkinsonian-Hyperpyrexia Syndrome, Malignant Catatonia, intrathecal baclofen withdrawal, Malignant Hyperthermia, Stiff Man Syndrome and Irukandji Syndrome. In their worst forms, each of these syndromes are relatively rare, are treated by different medical specialties and show widely varying pathophysiology. Most are considered to be medical emergencies and share significant mortality rates. Previous authors have noted similarities between some of these conditions, prompting the suggestion that a single common mechanism may underlie their clinical presentation. However, the development of such an integrative model has not occurred. This paper presents a short review of the clinical syndromes, grouped by the location of pathology and mechanism of action. From this background, an integrative framework termed the excitatory:inhibitory ratio (EIR) model is presented. The EIR model consists of two inter-related networks operating at spinal and brainstem levels. The model is evaluated against pre-clinical scientific research, known pathways, each disorder's pathophysiology (where this is known) and variable severity, and used to explain the reasons behind the efficacy of current treatment regimes. Circumstantial evidence for an expanded aetiology for Malignant Hyperthermia is provided and generic treatment strategies for a number of other conditions are suggested. Finally, minor modifications to this model provide a basis to begin to explain less severe, regional "overlap" syndromes.
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Affiliation(s)
- Ian J Baguley
- Brain Injury Rehabilitation Service, Westmead Hospital, P.O. Box 533, Westmead, Wentworthville, NSW 2145, Australia.
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353
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Escher M, Daali Y, Chabert J, Hopfgartner G, Dayer P, Desmeules J. Pharmacokinetic and pharmacodynamic properties of buprenorphine after a single intravenous administration in healthy volunteers: a randomized, double-blind, placebo-controlled, crossover study. Clin Ther 2007; 29:1620-31. [PMID: 17919544 DOI: 10.1016/j.clinthera.2007.08.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2007] [Indexed: 10/22/2022]
Abstract
BACKGROUND Buprenorphine is used as an analgesic for postoperative and chronic pain. The usual sublingual dose is 0.2 to 0.8 mg, and the usual parenteral dose is 0.3 mg for acute postoperative pain. The pharmacokinetic and related pharmacodynamic properties of buprenorphine at these doses have not been characterized. OBJECTIVE The aim of this study was to assess the pharmacokinetic properties of buprenorphine 0.002 mg/kg IV (0.15 mg/70 kg) and its antinociceptive and psychomotor effects. METHODS Healthy male volunteers received 0.002 mg/kg buprenorphine IV in a randomized, double-blind, placebo-controlled, crossover design. Blood samples were collected at 0.5, 1, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, and 8 hours for the determination of plasma concentrations. Pharmacokinetic parameters were estimated by a compartmental model using specialized software. Antinociceptive and psychomotor effects were determined for 8 hours. Quantitative sensory testing with thermal and electrical (nociceptive flexion RIII reflex) stimulations was performed. The cold pressor test was used to assess pain tolerance to a tonic, intense pain stimulation. Psychomotor performance was assessed by the digit symbol substitution test (DSST). Participants also rated sedation on an 11-point numeric scale (0 = none to 10 = severe). A selective liquid chromatography-tandem mass spectrometry assay was developed for the determination of buprenorphine; the limit of quantification was 0.05 ng/mL using a 0.25-mL plasma aliquot. Participants were instructed to report adverse effects, which were recorded for type, time of onset, seriousness, and duration. RESULTS The study enrolled 12 participants, all of whom were white. Mean (SD) age was 26 (3.5) years, and mean weight was 67 (9) kg. None of the participants had a history of opiate abuse. Buprenorphine significantly increased the objective (nociceptive flexion RIII reflex) and subjective pain thresholds for >4 hours and pain tolerance (cold pressor test) for 2 hours. The mean (SD) RIII reflex threshold and subjective threshold at baseline were 31.6 (9.5) mA and 45.5 (22.3) mA, respectively. The maximum increases (mean [SD]) were +14.1 (17.5) mA for the RIII reflex (P = 0.02) and +24.2 (21.7) mA for the subjective threshold (P = 0.02), corresponding to mean (SEM) percentages of 53.7% (20.2%) and 74.7% (20.4%) of the baseline values, respectively. The maximum increases were observed at 120 minutes for both measures. The effect of buprenorphine on pain tolerance peaked at 30 minutes. Mean (SEM) latency before withdrawal of the hand was 69 (10) seconds, corresponding to a mean increase of 63.8% (14.4%) from baseline (P = 0.003). Buprenorphine had a significant effect on the DSST. The mean maximum decrease in the total number of symbols drawn was -6 (14.5%; P = 0.005) at 1 hour. The participants reported high levels of sedation: at peak effect (120 minutes), mean scores increased from 2.9 to 6.4 (SEM 0.7) (P = 0.005). Levels returned to baseline values by the end of the session, unlike for the nociceptive tests. The onset of effects occurred during the distribution phase for all the measures, and their duration was observed across a wide range of concentrations during the elimination phase. The most likely explanation for this finding is the high affinity of buprenorphine at mu-opioid receptors, and possibly distribution to the brain. Buprenorphine t(l/2) was 2.75 hours. A secondary peak in concentration was observed at 90 minutes, suggesting enterohepatic circulation of buprenorphine. A 2-compartment model adequately described buprenorphine pharmacokinetics. CONCLUSIONS A clinically relevant analgesic dose of 0.002 mg/kg (0.15 mg/70 kg) of buprenorphine had a significant effect on nociception and psychomotor performance in these healthy male volunteers. A 2-compartment model satisfactorily characterized buprenorphine pharmacokinetics, and we found evidence of enterohepatic circulation.
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Affiliation(s)
- Monica Escher
- Division of Clinical Pharmacology and Toxicology, Geneva University Hospitals, Geneva, Switzerland.
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354
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Garcia-Perez E, Mazzoni A, Torre V. Spontaneous electrical activity and behavior in the leech hirudo medicinalis. Front Integr Neurosci 2007; 1:8. [PMID: 18958236 PMCID: PMC2526008 DOI: 10.3389/neuro.07.008.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Accepted: 11/14/2007] [Indexed: 12/03/2022] Open
Abstract
In the absence of external stimuli, animals explore the environment by performing irregular movements, but the neuronal mechanisms underlying this arrhythmic motion are largely unknown. In this paper, we studied the relationship between the spontaneous neuronal activity in the leech (Hirudo medicinalis) and its behavior. We analyzed the electrical activity of isolated ganglia, chains of two connected ganglia, and semi-intact preparations. The spontaneous electrical activity in ganglia was characterized by the occurrence of irregular bursts of spikes with variable duration and size. Properties of these bursts were modified by synaptic inputs arriving from the neighboring ganglia and from the two primitive brains located in the head and tail. In fact, in semi-intact preparations, unusually large bursts of spikes occurring spontaneously were recorded and caused the leech to move even in the absence of any external sensory stimulation. These large bursts appear to act as internal triggers controlling the spontaneous leech behavior and determining the duration of stereotypical motor patterns.
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355
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McIntyre D, Kavussanu M, Ring C. Effects of arterial and cardiopulmonary baroreceptor activation on the upper limb nociceptive flexion reflex and electrocutaneous pain in humans. Pain 2007; 137:550-555. [PMID: 18037241 DOI: 10.1016/j.pain.2007.10.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 09/17/2007] [Accepted: 10/15/2007] [Indexed: 11/18/2022]
Abstract
Attenuation of the lower limb nociceptive flexion reflex (NFR) during the cardiac cycle has been attributed to inhibition of sensorimotor function by arterial baroreceptor activation. It has been proposed that cardiopulmonary baroreceptors might have similar inhibitory effects. This study examined the effects of arterial and cardiopulmonary baroreceptor stimulation on nociceptive responding in the upper limb by delivering electrocutaneous stimuli to the ulnar nerve at 0, 150, 300, 450, or 600 ms after the R-wave of the electrocardiogram while participants lay supine with their legs raised or lowered. Nociceptive responding varied in a quadratic manner with phase of the cardiac cycle; responses were lowest at R+450 ms. Nociceptive responding and pain ratings did not differ between postures suggesting no cardiopulmonary effects. This phasic modulation of the upper limb withdrawal response provides further support for arterial baroreceptor-mediated inhibition of nociceptive transmission.
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Affiliation(s)
- David McIntyre
- International Centre for Health and Exercise Research, University of Birmingham, Birmingham B15 2TT, UK
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356
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Slater R, Fitzgerald M, Meek J. Can cortical responses following noxious stimulation inform us about pain processing in neonates? Semin Perinatol 2007; 31:298-302. [PMID: 17905184 DOI: 10.1053/j.semperi.2007.07.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The measurement of pain in neonates presents a unique challenge. Infants, unable to describe pain verbally, rely on caregivers to assess and manage pain on their behalf. Behavioral and physiological indicators, often used in pain assessment in this population, are assumed surrogate measures of pain processing; however, it has not been proven that these outcome measures correlate with perceived pain, which requires higher cortical processing. Recent studies in neonates have used near-infrared spectroscopy to measure the cortical responses to nociception. The magnitude of these responses can be compared with current clinical pain assessment measures, which provides the opportunity to assess whether these measures are a true reflection of cortical pain processing. This review discusses the use of near-infrared spectroscopy and compares it with alternative pain assessment measures in this vulnerable population.
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Affiliation(s)
- Rebeccah Slater
- Department of Anatomy and Developmental Biology, University College London, London, United Kingdom.
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357
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Edwards L, Ring C, France CR, al'Absi M, McIntyre D, Carroll D, Martin U. Nociceptive flexion reflex thresholds and pain during rest and computer game play in patients with hypertension and individuals at risk for hypertension. Biol Psychol 2007; 76:72-82. [PMID: 17686566 PMCID: PMC2042542 DOI: 10.1016/j.biopsycho.2007.06.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 06/21/2007] [Accepted: 06/24/2007] [Indexed: 10/23/2022]
Abstract
Supraspinal pain modulation may explain hypertensive hypoalgesia. We compared nociceptive flexion reflex (NFR) thresholds and pain during rest and computer game play in hypertensives and normotensives (Experiment 1) and normotensives with and without hypertensive parents (Experiment 2). The game was selected to modulate activity in pain pathways. NFR thresholds did not differ between groups during rest or game play. Pain ratings never differed between hypertensives and normotensives, whereas individuals with hypertensive parents reported less pain during the first two NFR assessments, compared to those without. NFR thresholds and pain were reduced by game play compared to rest. The failure of game play to differentially modulate NFR thresholds or associated pain reports between groups argues against enhanced supraspinal modulation of nociception and pain in hypertensives and those at increased risk for hypertension.
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Affiliation(s)
- Louisa Edwards
- International Centre for Health and Exercise Research, University of Birmingham, Birmingham B15 2TT, UK.
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358
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Michel J, van Hedel HJA, Dietz V. Facilitation of spinal reflexes assists performing but not learning an obstacle-avoidance locomotor task. Eur J Neurosci 2007; 26:1299-306. [PMID: 17767507 DOI: 10.1111/j.1460-9568.2007.05759.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of this study was to investigate spinal reflex (SR) modulation during the performance and learning of a precision locomotor task. Healthy subjects had to minimize foot clearance when repeatedly stepping on a treadmill over a randomly approaching obstacle. The subjects walked with reduced vision and were informed about the approaching obstacle and task performance by acoustic warning and feedback signals, respectively. SRs were randomly evoked by tibial nerve stimulation (with non-nociceptive and nociceptive stimulus intensity) during the mid-stance phase in both normal and pre-obstacle stepping. Foot clearance and electromyographic activity of the tibialis anterior and biceps femoris muscles of the right leg were analysed. Only if a delay was introduced between warning signal and nerve stimulation, was the SR amplitude in both muscles enhanced prior to obstacle steps compared with normal steps for both stimulus intensities. Thus, the reflex enhancement depended on the subject's awareness of the approaching obstacle. Improved performance was reflected in a decreased foot clearance, but did not correlate with the course of SR amplitude. It is concluded that obstacle stepping is associated with a facilitation of SR pathways, probably by supraspinal drive. This facilitation might provide assistance in safe obstacle stepping, e.g. to compensate quickly if resistance is encountered.
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Affiliation(s)
- J Michel
- Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland.
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359
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Rhudy JL, Williams AE, McCabe KM, Russell JL, Maynard LJ. Emotional control of nociceptive reactions (ECON): do affective valence and arousal play a role? Pain 2007; 136:250-261. [PMID: 17703886 DOI: 10.1016/j.pain.2007.06.031] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Revised: 06/06/2007] [Accepted: 06/25/2007] [Indexed: 11/17/2022]
Abstract
Prior research suggests emotional picture-viewing modulates motoric (nociceptive flexion reflex), autonomic (skin conductance response, heart rate acceleration), and subjective (pain rating) reactions to noxious electrodermal stimulation. The present study sought to determine whether emotional valence and arousal contribute to nociception modulation. To do so, pictures varying in emotional content (erotica, food, neutral, loss, attack) were chosen to manipulate emotional valence (pleasant=erotic and food; unpleasant=loss and attack) and arousal (low=food and loss; moderate=erotica and attack). Pictures were presented in pseudorandom order to elicit emotional processing while noxious electric stimulations were delivered to the sural nerve. Nociceptive flexion reflex (NFR) magnitude, skin conductance response (SCR), heart rate (HR) acceleration, and subjective pain ratings to each stimulation were measured, standardized, averaged by picture content, and analyzed. Results suggested that picture-viewing explained 52% of the variance in the multivariate combination of the nociceptive reactions and modulated them in parallel. Pleasant pictures inhibited reactions, whereas unpleasant pictures enhanced them. However, only erotica and attack pictures elicited significant modulation relative to neutral pictures, suggesting arousal also contributed. An exploratory multilevel analysis also supported this conclusion. Together, these data suggest emotional control of nociceptive reactions (ECON) is associated with a valence-by-arousal interaction. Implications of these findings for how emotional picture-viewing can be used to study supraspinal modulation are discussed.
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Affiliation(s)
- Jamie L Rhudy
- Department of Psychology, The University of Tulsa, 600 South College Avenue, Tulsa, OK 74104, USA
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360
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Martin F, Fletcher D, Chauvin M, Bouhassira D. Constitutive cyclooxygenase-2 is involved in central nociceptive processes in humans. Anesthesiology 2007; 106:1013-8. [PMID: 17457134 PMCID: PMC3984587 DOI: 10.1097/01.anes.0000265162.39932.33] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Prostaglandins play a major role in inflammation and pain. They are synthesized by the two cyclooxygenase (COX) isoforms: COX-1, which is expressed constitutively in many cell types, and COX-2, which is induced at the site of inflammation. However, unlike peripheral tissues, COX-2 is expressed constitutively in the central nervous system and may play a role in nociceptive processes. The current study aimed to investigate the role of constitutive COX-2 in the spinal transmission of nociceptive signals in humans. METHODS The authors used 12 healthy volunteers to compare the effects of the specific COX-2 inhibitor sodium parecoxib (1 mg/kg) or placebo, administered intravenously in a double-blind and crossover fashion, on the electrophysiologic recordings of the nociceptive flexion (RIII) reflex. The RIII reflex is an objective psychophysiologic index of the spinal transmission of nociceptive signals and was recorded from the biceps femoris after electrical stimulation of the sural nerve. Two experiments, 7 days apart, were conducted in each volunteer. On each experimental day, the effects of parecoxib or placebo were tested on (1) the RIII reflex threshold, (2) the stimulus-response curves of the reflex up to the tolerance threshold (frequency of stimulation: 0.1 Hz), and (3) the progressive increase of the reflex and pain sensations (i.e., "windup" phenomenon) induced by a series of 15 stimulations at a frequency of 1 Hz (intensity 20% above RIII threshold). RESULTS Parecoxib, but not placebo, significantly reduced the slope of the stimulus-response curve, suggesting a reduction in the gain of the spinal transmission of nociceptive signals. By contrast, the windup phenomenon was not significantly altered after administration of parecoxib or placebo. CONCLUSIONS This study shows that constitutive COX-2 modulates spinal nociceptive processes and that the antiinflammatory and antinociceptive actions of COX-2 inhibitors are not necessarily related.
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Affiliation(s)
- Frédéric Martin
- Physiopathologie et Pharmacologie Clinique de la Douleur
INSERM : U792Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)Hopital Ambroise Pare 9 Avenue Charles de Gaulle 92100 Boulogne Billancourt, FR
| | - Dominique Fletcher
- Physiopathologie et Pharmacologie Clinique de la Douleur
INSERM : U792Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)Hopital Ambroise Pare 9 Avenue Charles de Gaulle 92100 Boulogne Billancourt, FR
- Service d'Anesthésie
Assistance Publique - Hôpitaux de Paris (AP-HP)Hôpital Raymond Poincaré92380 Garches, FR
| | - Marcel Chauvin
- Physiopathologie et Pharmacologie Clinique de la Douleur
INSERM : U792Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)Hopital Ambroise Pare 9 Avenue Charles de Gaulle 92100 Boulogne Billancourt, FR
- Service d'Anesthésie
Assistance Publique - Hôpitaux de Paris (AP-HP)Hôpital Raymond Poincaré92380 Garches, FR
| | - Didier Bouhassira
- Physiopathologie et Pharmacologie Clinique de la Douleur
INSERM : U792Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)Hopital Ambroise Pare 9 Avenue Charles de Gaulle 92100 Boulogne Billancourt, FR
- * Correspondence should be addressed to: Didier Bouhassira
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361
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Ge HY, Collet T, Mørch CD, Arendt-Nielsen L, Andersen OK. Depression of the human nociceptive withdrawal reflex by segmental and heterosegmental intramuscular electrical stimulation. Clin Neurophysiol 2007; 118:1626-32. [PMID: 17507291 DOI: 10.1016/j.clinph.2007.04.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Revised: 04/12/2007] [Accepted: 04/15/2007] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To investigate the effects of intramuscular electrical conditioning in the modulation of nociceptive withdrawal reflex (NWR) and further to determine what muscle afferents are involved in the modulation of the nociceptive withdrawal reflex and the sites along the reflex pathway where the NWR modulation occurs in healthy humans. METHODS The NWR elicited by a cutaneous test stimulus to the dorsal foot was modulated by a short (21 ms) intramuscular conditioning electrical stimulus at two times the pain threshold. At varying conditioning-test stimulus intervals, segmental conditioning stimulus was applied in the tibialis anterior muscle ipsilateral and contralateral to the test stimulus, and heterosegmental conditioning stimulus was applied in the contralateral trapezius muscle to modulate the NWR. Non-painful and painful intramuscular conditioning stimuli were also used to modulate the NWR and the soleus H-reflex. RESULTS The NWR was depressed by preceding intramuscular conditioning stimuli, with a degree that depended on the conditioning-test stimulus intervals and on the conditioning site. Segmental conditioning depressed the NWR more quickly and gave a longer duration (15-1500 ms), and larger magnitude than heterosegmental conditioning, which depressed the NWR in a short temporal window (80-100 ms). No difference was seen in the magnitude of the NWR depression between the painful and non-painful intramuscular stimuli, and the soleus H-reflex was not affected. CONCLUSIONS Our results suggest that segmental and heterosegmental conditionings of NWR are mediated by myelinated muscle afferents engaging central inhibitory mechanisms rather than direct changes in the excitability of motor neurons. SIGNIFICANCE The therapeutic effects of electrotherapy could involve these mechanisms in the treatment of muscle pain syndromes.
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Affiliation(s)
- Hong-You Ge
- Laboratory for Experimental Pain Research, Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark
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362
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Berkowitz A. Spinal interneurons that are selectively activated during fictive flexion reflex. J Neurosci 2007; 27:4634-41. [PMID: 17460076 PMCID: PMC6673003 DOI: 10.1523/jneurosci.5602-06.2007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2006] [Revised: 03/20/2007] [Accepted: 03/21/2007] [Indexed: 11/21/2022] Open
Abstract
Behavioral choices in invertebrates are mediated by a combination of shared and specialized circuitry, including neurons that are inhibited during competing behaviors. Less is known, however, about the neural mechanisms of behavioral choice in vertebrates. The spinal cord can appropriately select among several types of limb movements, including limb withdrawal (flexion reflex), scratching, and locomotion, and thus is conducive to examination of vertebrate mechanisms of behavioral choice. Flexion reflex can interrupt and reset the rhythm of scratching and locomotion, suggesting that a combination of shared and specialized circuitry contributes to these behaviors, but little is known about the interneurons involved. Here, I used in vivo intracellular recording and dye injection to identify a group of spinal interneurons that are strongly activated during fictive flexion reflex but inhibited during fictive scratching and fictive swimming. These flexion-selective interneurons are typically rhythmically hyperpolarized during fictive scratching and fictive swimming. This hyperpolarization can be maximal during the ipsilateral hip flexor bursts of rhythmic limb motor patterns, although these cells are strongly activated during the ipsilateral hip flexor bursts of fictive flexion reflex. Thus, these interneurons are relatively specialized for fictive limb withdrawal, rather than contributing to the hip flexor phase of multiple types of limb movements. These flexion-selective cells are physiologically and morphologically distinguishable from a recently described group of spinal interneurons (transverse interneurons) that are strongly activated during both fictive flexion reflex and fictive scratching. Thus, spinal interneurons with distinct behavioral roles may to some extent be morphologically distinguishable.
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Affiliation(s)
- Ari Berkowitz
- Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019, USA.
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363
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Rhudy JL, Maynard LJ, Russell JL. Does In Vivo Catastrophizing Engage Descending Modulation of Spinal Nociception? THE JOURNAL OF PAIN 2007; 8:325-33. [PMID: 17140855 DOI: 10.1016/j.jpain.2006.10.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 09/18/2006] [Accepted: 10/01/2006] [Indexed: 10/23/2022]
Abstract
UNLABELLED Prior research has found that pain catastrophizing measured before pain testing is not correlated with the nociceptive flexion reflex (NFR) threshold (a measure of spinal nociception), suggesting that catastrophizing does not alter pain through descending modulatory mechanisms. However, recent evidence suggests that in vivo catastrophizing (measured during or after pain testing) is a better predictor of pain outcomes. In the present study, NFR threshold and pain sensation ratings were assessed in 78 healthy participants by delivering electric stimulations to the sural nerve. After pain testing, participants were asked to rate their affective reaction (displeasure, arousal) to electric stimuli and to report on their pain catastrophizing. Hierarchical regression analyses controlling for participant sex, pre-experiment affect, depressive symptoms, and self-efficacy were used to predict pain-related outcomes (NFR threshold, pain sensation, displeasure ratings, arousal ratings) from in vivo catastrophizing scores. Results indicated that in vivo catastrophizing was related to pain sensation but not to NFR thresholds or arousal reactions. The relation between in vivo catastrophizing and displeasure ratings was not significant after other variables were controlled. These data support prior research suggesting that catastrophizing does not alter pain by engaging descending modulatory mechanisms. PERSPECTIVE Pain catastrophizing is an important psychological predictor of pain and pain-related functioning. The present study confirms prior reports suggesting that catastrophizing does not work by engaging mechanisms that alter pain transmission in the spinal cord before the signal travels to the brain.
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Affiliation(s)
- Jamie L Rhudy
- Department of Psychology, The University of Tulsa, Tulsa, Oklahoma 74104, USA.
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364
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Andersen OK. Studies of the organization of the human nociceptive withdrawal reflex. Focus on sensory convergence and stimulation site dependency. Acta Physiol (Oxf) 2007; 189 Suppl 654:1-35. [PMID: 17439638 DOI: 10.1111/j.1748-1716.2007.01706.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- O K Andersen
- Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Denmark
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365
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Knikou M. Hip-phase-dependent flexion reflex modulation and expression of spasms in patients with spinal cord injury. Exp Neurol 2007; 204:171-81. [PMID: 17125766 PMCID: PMC1810565 DOI: 10.1016/j.expneurol.2006.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Revised: 10/06/2006] [Accepted: 10/15/2006] [Indexed: 11/21/2022]
Abstract
The flexion reflex in human spinal cord injury (SCI) is believed to incorporate interneuronal circuits that consist elements of the stepping generator while ample evidence suggest that hip proprioceptive input is a controlling signal of locomotor output. In this study, we examined the expression of the non-nociceptive flexion reflex in response to imposed sinusoidal passive movements of the ipsilateral hip in human SCI. The flexion reflex was elicited by low-intensity stimulation (300 Hz, 30 ms pulse train) of the right sural nerve at the lateral malleolus, and recorded from the tibialis anterior (TA) muscle. Sinusoidal hip movements were imposed to the right hip joint at 0.2 Hz by a Biodex system while subjects were supine. The effects of leg movement on five leg muscles along with hip, knee, and ankle joint torques were established simultaneously with the modulation pattern of the flexion reflex during hip oscillations. Phase-dependent modulation of the flexion reflex was present during hip movement, with the reflex to be significantly facilitated during hip extension and suppressed during hip flexion. The phase-dependent flexion reflex modulation coincided with no changes in TA pre- and post-stimulus background ongoing activity during hip extension and flexion. Reflexive muscle and joint torque responses, induced by the hip movement and substantiated by excitation of flexion reflex afferents, were entrained to specific phases of hip movement. Joint torque responses were consistent with multi-joint spasmodic muscle activity, which was present mostly during the transition phase of the hip from flexion to extension and from mid- to peak extension. Our findings provide further evidence on the interaction of hip proprioceptors with spinal interneuronal circuits engaged in locomotor pathways, and such interaction should be considered in rehabilitation protocols employed to restore sensorimotor function in people with SCI.
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Affiliation(s)
- Maria Knikou
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60610, USA.
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366
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Mørch CD, Andersen OK, Graven-Nielsen T, Arendt-Nielsen L. Nociceptive withdrawal reflexes evoked by uniform-temperature laser heat stimulation of large skin areas in humans. J Neurosci Methods 2007; 160:85-92. [PMID: 16996136 DOI: 10.1016/j.jneumeth.2006.08.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 08/23/2006] [Accepted: 08/24/2006] [Indexed: 11/16/2022]
Abstract
Nociceptive withdrawal reflexes (NWR) were evoked by brief (200 ms) painful CO(2) laser stimulation at five intensities (1.2, 1.4, 1.6, 1.8, and 2.0 x pain threshold) applied to nine sites (2 cm(2)) separated by 1.7 cm on the dorsal side of the foot and anterior part of the lower leg of 14 healthy volunteers. The purpose of the study was to investigate the characteristics of NWRs evoked by a natural stimulation modality. The reflexes were measured as the electromyographic response from the iliopsoas (ILI), quadriceps vastus lateralis (QVL), biceps femoris (BF), tibialis anterior (TA), and soleus (SOL) muscles. Stimulus-response relationships between heat intensity and the reflex magnitude and correlation between perceived pain intensity and reflex magnitude were observed in the ILI, QVL, BF, and TA but not the SOL. No significant differences in reflex magnitude were found between the stimulation sites. NWRs were evoked more often in flexor muscles than extensor muscles, indicating a non-site-specific reflex organization. The paper presents a new method to evoke NWRs by uniform-temperature laser heat stimulation of large skin areas in humans. These heat evoked reflexes had a stimulus-response relationship.
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Affiliation(s)
- Carsten Dahl Mørch
- Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark.
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367
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Goffaux P, Redmond WJ, Rainville P, Marchand S. Descending analgesia--when the spine echoes what the brain expects. Pain 2007; 130:137-43. [PMID: 17215080 DOI: 10.1016/j.pain.2006.11.011] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 11/12/2006] [Accepted: 11/21/2006] [Indexed: 10/23/2022]
Abstract
Changes in pain produced by psychological factors (e.g., placebo analgesia) are thought to result from the activity of specific cortical regions. However, subcortical nuclei, including the periaqueductal gray and the rostroventral medulla, also show selective activation when subjects expect pain relief. These brainstem regions send inhibitory projections to the spine and produce diffuse analgesic responses. Regrettably the precise contribution of spinal mechanisms in predicting the strength of placebo analgesia is unknown. Here, we show that expectations regarding pain radically change the strength of spinal nociceptive responses in humans. We found that contrary to expectations of analgesia, expectations of hyperalgesia completely blocked the analgesic effects of descending inhibition on spinal nociceptive reflexes. Somatosensory-evoked brain potentials and pain ratings further confirmed changes in spino-thalamo-cortical responses consistent with expectations and with changes in the spinal response. These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice.
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Affiliation(s)
- Philippe Goffaux
- Université de Sherbrooke, Faculté de Médecine, Sherbrooke, Que., Canada J1H 5N4
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368
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Brackett NL, Ibrahim E, Krassioukov A, Lynne CM. Systemic naloxone infusion may trigger spasticity in patients with spinal cord injury: case series. J Spinal Cord Med 2007; 30:272-5. [PMID: 17684894 PMCID: PMC2031956 DOI: 10.1080/10790268.2007.11753936] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVE Three patients with spinal cord injury (SCI) and 3 able-bodied (AB) patients were infused with naloxone during a study to examine their neuroendocrine function. An unanticipated side effect occurred during the naloxone infusion. All 3 patients with SCI, but none of the AB patients, experienced profoundly increased spasticity during the naloxone infusion. Our report describes this side effect, which has potential implications for the clinical treatment or scientific evaluation of individuals with SCI. METHODS All patients were in good general health and medication free for 11 days or longer before the study. Each patient was placed on a 30-hour protocol to analyze pulsatile release of gonadotropins. Physiologic saline was intravenously infused on day 1 to serve as a control period for naloxone infusion on day 2. RESULTS AB patients experienced no muscle spasm activity or any other side effects at any time during the study. In contrast, all 3 patients with SCI experienced a profoundly increased frequency and duration of spasticity in muscles innervated by the nerve roots caudal to their level of injury. In all 3 patients with SCI, spasticity increased only during the period of naloxone infusion. Within 1 hour of stopping naloxone, spasticity returned to baseline levels. CONCLUSIONS Naloxone infusion produced a differential effect on the muscle activity of men with SCI compared to AB men with intact spinal circuits. Consistent with previous studies, the results of this study indicate a relationship between opioid neuromodulation and spasticity after SCI.
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Affiliation(s)
- Nancy L Brackett
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Lois Pope Life Center, Room 1-27, 1095 NW 14th Terrace, Miami, FL 33136, USA.
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369
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Del Santo F, Gelli F, Spidalieri R, Rossi A. Corticospinal drive during painful voluntary contractions at constant force output. Brain Res 2007; 1128:91-8. [PMID: 17134682 DOI: 10.1016/j.brainres.2006.09.039] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 09/13/2006] [Accepted: 09/13/2006] [Indexed: 11/22/2022]
Abstract
In the voluntary contractions, output force can be maintained constant although the inhibitory influences exerted by pain on muscle activity. We investigated changes in the spontaneous and evoked activity of the abductor digiti minimi muscle (ADM) and the biceps brachii muscle (BIC) in healthy volunteers during constant force noxious contraction, resulting from chemically activated nociceptive afferents. EMG-force relationship, motor-evoked response (MEP) to transcranial magnetic stimulation and determinism (DET) of surface EMG signals during constant force contraction was analyzed before, during and after chemically induced tonic activation of their nociceptive afferents. Under constant force contraction, amplitude of surface EMG signal decreased in BIC and increased in ADM during pain with respect to control condition. In both muscles, the size of motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) of the primary motor cortex was significantly higher during pain than in control. Level of determinism extracted from surface EMG signal by non-linear method was similarly and significantly increased in both muscles during pain stimulation. Finally, nociceptive stimulation caused a decline in steadiness of the force exerted by ADM and BIC. These results are interpreted in terms of increased corticospinal synchronizing inputs. The possibility that it may play a role in governing force production to counteract pain inhibitory influences on motor system is considered.
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Affiliation(s)
- Francesco Del Santo
- Unit of Clinical Neurophysiology, Department of Neurological and Behavioural Sciences, University of Siena, Viale Bracci 1, 53100 Siena, Italy
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370
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Rhudy JL, McCabe KM, Williams AE. Affective modulation of autonomic reactions to noxious stimulation. Int J Psychophysiol 2007; 63:105-9. [PMID: 17049399 DOI: 10.1016/j.ijpsycho.2006.09.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Revised: 09/05/2006] [Accepted: 09/05/2006] [Indexed: 10/24/2022]
Abstract
Research suggests that emotion modulates spinal nociception and pain; however, there is limited evidence that other objective, nociceptive reactions are modulated. This study examined the impact of affective picture-viewing on autonomic reactions (skin conductance response, heart rate acceleration) resulting from noxious electric stimulations to the sural nerve. Pictures varying in affective valence (unpleasant, neutral, pleasant) were presented during which noxious stimulations were delivered. Skin conductance response and short-latency heart rate acceleration following each stimulation was calculated and averaged by picture valence. Results suggested that autonomic reactions were modulated in parallel. Specifically, reactions were smaller during pleasant pictures than unpleasant pictures, although unpleasant pictures did not result in significant facilitation relative to neutral pictures. The valence linear trend explained 26% of the variance in the multivariate combination of the reactions, suggesting emotion does modulate autonomic reactions to nociception. These results suggest that SCR and HR acceleration are outcomes that can be assessed together with NFR and pain report during picture-viewing to study affective modulation of spinal (NFR), supraspinal (SCR, HR acceleration), and subjective (pain report) nociceptive reactions.
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Affiliation(s)
- Jamie L Rhudy
- Department of Psychology, The University of Tulsa, 600 South College, Tulsa, OK 74104, USA.
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371
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Rhudy JL, Williams AE, McCabe KM, Rambo PL, Russell JL. Emotional modulation of spinal nociception and pain: The impact of predictable noxious stimulation. Pain 2006; 126:221-33. [PMID: 16890356 DOI: 10.1016/j.pain.2006.06.027] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Accepted: 06/26/2006] [Indexed: 11/21/2022]
Abstract
Recent evidence suggests that emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. The present study attempted to replicate these findings and determine the effect of noxious stimulus predictability. Participants viewed pictures from the International Affective Picture System (IAPS), during which pain and nociceptive flexion reflexes (NFR) were elicited by electric shocks delivered to the sural nerve. For half of the participants (n=25) shocks were preceded by a cue (predictable), whereas the other half received no cue (unpredictable). Results suggested emotion was successfully induced by pictures, but the effect of picture-viewing on the NFR was moderated by the predictability of the shocks. When shock was unpredictable, spinal nociception (NFR) and pain ratings were modulated in parallel. Specifically, pain and NFR magnitudes were lower during pleasant emotions and higher during unpleasant emotions. However, when shocks were predictable, only pain was modulated in this way. NFRs from predictable shocks were not altered by pictures. Further, exploratory analyses found that pain ratings, but not NFRs, were lower during predictable shocks. These data suggest emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. However, descending modulation could not be detected in NFRs resulting from predictable noxious stimuli. Although preliminary, this study implies that separate mechanisms are responsible for emotional modulation of nociception at spinal vs. supraspinal levels, and that predictable noxious events may disengage modulation at the spinal level. The current paradigm could serve as a useful tool for studying descending modulation.
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Affiliation(s)
- Jamie L Rhudy
- Department of Psychology, The University of Tulsa, 600 South College Ave., Tulsa, OK 74104, USA.
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372
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Kolb TFB, Lachauer S, Schoch B, Gerwig M, Timmann D, Kolb FP. Comparison of the electrically evoked leg withdrawal reflex in cerebellar patients and healthy controls. Exp Brain Res 2006; 177:493-508. [PMID: 17051385 DOI: 10.1007/s00221-006-0706-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 08/30/2006] [Indexed: 11/25/2022]
Abstract
The aim of this study was to analyze the contribution of the cerebellum in the performance of the lower limb withdrawal reflexes. This has been accomplished by comparing the electrically evoked responses in cerebellar patients (CBL) with those in sex- and age-matched healthy control subjects (CTRL). The stimulus was applied to the subjects' medial plantar nerve in four blocks of ten trials each with switching the stimulus from one leg to the other after each block. Responses of the main muscle groups (tibial muscle: TA; gastrocnemius muscle: GA; rectus femoris muscle: RF; biceps femoris muscle: BI) of both legs were recorded during each stimulus. The group of CBL patients consisted of both focally lesioned patients (CBLf) and patients presenting a diffuse degenerative pathology (CBLd). (1) For the withdrawal reflex in CTRL subjects, responses were observed in distal and proximal muscles of the ipsilateral side and corresponding concomitant responses on the side contralateral to the stimulation, whereas in CBL patients responses were restricted primarily to distal muscles, particularly the TA of the ipsilateral, i.e. the stimulated, side. (2) The sequence of activation of the different distal and proximal muscles ipsilateral to the stimulation, derived from latencies and times-to-peak, was for the CTRL group: TA-GA-BI-RF. This sequence was found also in the CBLf patients on their unaffected side. However, on their affected side CBLf patients showed very early GA activation, almost simultaneously with TA and RF activations and before BI activation. RF activation before BI activation was also found in CBLd. In the latter group, GA was activated after RF but before BI with all responses typically delayed. (3) The general pattern of the electrically evoked lower limb reflex consisted of an early, excitatory F1 component and a later, excitatory F2 component of larger amplitude observed in the CTRL subjects and the CBLd patients. In contrast to this pattern CBLf patients exhibited large F1 components followed by small F2 components. (4) The characteristic differences in the withdrawal reflex responses of cerebellar patients depended on the type of the lesion, providing evidence for an important involvement of the cerebellum in the control of the performance of withdrawal reflexes.
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Affiliation(s)
- T F B Kolb
- Institute of Physiology, University of Munich, Pettenkoferstr. 12, 80336 München, Germany
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373
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Laser literature watch. Photomed Laser Surg 2006; 24:424-53. [PMID: 16875454 DOI: 10.1089/pho.2006.24.424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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374
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Hoving MA, van Kranen-Mastenbroek VHJM, van Raak EPM, Spincemaille GHJJ, Hardy ELM, Vles JSH. Placebo controlled utility and feasibility study of the H-reflex and flexor reflex in spastic children treated with intrathecal baclofen. Clin Neurophysiol 2006; 117:1508-17. [PMID: 16759902 DOI: 10.1016/j.clinph.2006.04.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Revised: 04/06/2006] [Accepted: 04/11/2006] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To evaluate feasibility and utility of the soleus H-reflex and tibialis anterior flexor reflex (FR) in identifying spinal cord neuronal response to intrathecal baclofen (ITB) in children with severe spastic cerebral palsy. METHODS During a randomized, double-blind, placebo-controlled dose-escalation test treatment, maximum H amplitude/maximum M amplitude (H/M ratio) and FR parameters were bilaterally recorded at baseline and 2-3 h after intrathecal bolus administration of placebo and increasing doses of baclofen until both an improvement in the individual treatment goal(s) and a one-point reduction on the Ashworth scale were observed. RESULTS Electrophysiological data of 14 children were studied. The H-reflex was feasible in 13 children, the FR threshold area in 9 and the FR, elicited with supramaximal stimulation, in only one child. After ITB, the H/M ratio significantly decreased (left: 0.67+/-0.47 to 0.15+/-0.18, P=0.005; right: 0.55+/-0.32 to 0.14+/-0.19, P=0.002) without placebo effect. FR threshold area after ITB, only decreased significantly in children not taking oral baclofen (left: 146+/-53 to 41+/-54 mV ms, P=0.000; right: 156+/-80 to 66+/-48 mV ms, P=0.002). CONCLUSIONS This is the first randomized, double-blind, placebo-controlled dose-escalation study in spastic children demonstrating the soleus H-reflex to be a feasible and objective measure to quantify the decreasing motoneuron excitability in response to ITB bolus administration. Only in children not taking oral baclofen, FR threshold area can also be used as an objective outcome measure, yet feasibility is limited. SIGNIFICANCE We suggest introducing the H-reflex as the electrophysiological gold standard for the evaluation of the effect of ITB in spastic children.
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Affiliation(s)
- M A Hoving
- Department of Neurology, University Hospital Maastricht, P. Debyelaan 25, Postbus 5800, 6202 AZ Maastricht, The Netherlands.
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375
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Serrao M, Pierelli F, Don R, Ranavolo A, Cacchio A, Currà A, Sandrini G, Frascarelli M, Santilli V. Kinematic and electromyographic study of the nociceptive withdrawal reflex in the upper limbs during rest and movement. J Neurosci 2006; 26:3505-13. [PMID: 16571758 PMCID: PMC6673871 DOI: 10.1523/jneurosci.5160-05.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This study set out to evaluate nociceptive withdrawal reflex (NWR) excitability and the corresponding mechanical response in the upper limbs during rest and movement. We used a three-dimensional motion analysis system and a surface EMG system to record, in 10 healthy subjects, the NWR in eight upper limb muscles and the corresponding mechanical response in two experimental conditions: rest and movement (reaching for, picking up, and moving a cylinder). The NWR was elicited through stimulation of the index finger with trains of pulses delivered at multiples of the pain threshold (PT). We correlated movement types (reach-to-grasp, grasp-and-lift), movement phases (acceleration, deceleration), and muscle activity types (shortening, lengthening, isometric) with the presence/absence of the NWR (reflex-muscle pattern), with NWR size values, and with the mechanical responses. At rest, when the stimulus was delivered at 4x PT, the NWR was present, in all muscles, in >90% of trials, and the mechanical response consisted of wrist adduction, elbow flexion, and shoulder anteflexion. At this stimulus intensity, during movement, the reflex-muscle pattern, reflex size, and mechanical responses were closely modulated by movement type and phase and by muscle activity type. We did not find, during movement, significant correlations with the level of EMG background activity. Our findings suggest that a complex functional adaptation of the spinal cord plays a role in modulating the NWR in the transition from rest to movement and during voluntary arm movement freely performed in three-dimensional space. Study of the upper limb NWR may provide a window onto the spinal neural control mechanisms operating during movement.
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Affiliation(s)
- Mariano Serrao
- Department of Neurology and Otolaryngology, Santa Maria Goretti Hospital, Latina, La Sapienza, University of Rome, 00185 Rome, Italy.
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376
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Abstract
In normal life, activity-dependent plasticity occurs in the spinal cord as well as in the brain. Like CNS plasticity elsewhere, this spinal cord plasticity can occur at many neuronal and synaptic sites and by a variety of mechanisms. Spinal cord plasticity is prominent in postnatal development and contributes to acquisition of standard behaviors such as locomotion and rapid withdrawal from pain. Later on in life, spinal cord plasticity contributes to acquisition and maintenance of specialized motor skills, and to compensation for the peripheral and central changes associated with aging, disease, and trauma. Mastery of even the simplest behaviors is accompanied by complex spinal and supraspinal plasticity. This complexity is necessary, to preserve the full roster of behaviors, and is also inevitable, due to the ubiquity of activity-dependent plasticity in the CNS. Careful investigation of spinal cord plasticity is essential for understanding motor skills; and, because of the relative simplicity and accessibility of the spinal cord, is a logical and convenient starting point for exploring skill acquisition. Appropriate induction and guidance of activity-dependent plasticity in the spinal cord is likely to be a key part of the realization of effective new rehabilitation methods for spinal cord injuries, cerebral palsy, and other chronic motor disorders.
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Affiliation(s)
- Jonathan R Wolpaw
- Wadsworth Center, Laboratory of Nervous System Disorders, New York State Department of Health and State University of New York, Albany, NY 12201, USA.
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