Scientiﬁc presentations at the 2017 Annual Meeting / Scandinavian Journal of Pain 16 (2017) 165–188Previous studies have shown that CPM affects the nociceptive withdrawal reﬂex (NWR) threshold (RTh), typically assessed in onemuscle. However, the NWR activates not one but a group of synergistic muscles, which are recruited by common neural commandsto achieve the limb withdrawal. In this regard, synergy analysis canprovide the minimum coordinated recruitment of groups of muscles with speciﬁc activation balances that describe a movement.The aim was to assess how CPM modulate the global withdrawalstrategy of the lower limb expressed by synergy analysis.Methods: Sixteen healthy subjects received electrical stimulation in the arch of the foot at 2× RTh intensity assessed at the bicepsfemoris muscle, to elicit the NWR at three time points: before, during and after immersion of the hand in cold water at 2.6 ± 0.4◦ (coldpressor test, CPT) to trigger CPM. Electromyographic signals (EMG)were recorded from 2 distal muscles (tibialis anterior, soleus)and 2 proximal muscles (biceps femoris, rectus femoris). Musclesynergies were identiﬁed by a non-negative matrix factorizationalgorithm for the EMG envelope in the 60–180 ms post-stimulusinterval. Data were analyzed by a point-by-point Wilcoxon testusing a permutation strategy.Results: The overall withdrawal pattern was explained by twomain synergies (Syn1 and Syn2). Syn1 mainly contributes to EMGof distal muscles, whereas Syn2 contributes to EMG of proximalmuscles. During CPT, the magnitude of Syn2 was reduced in the160–180 ms post-stimulus interval (p < 0.05), whereas no changeswere found for Syn1.Conclusions: At least two synergies are required to explain theNWR. Furthermore, results suggest that CPM might differentiallyaffect proximal and distal muscles. Further analysis is needed toprovide additional information about the behavior of the individualmuscles.http://dx.doi.org/10.1016/j.sjpain.2017.04.036Application of miR-223 onto the dorsal nerveroots in rats induces hypoexcitability in thepain pathwaysA. Legfeldt a,b,∗ , D.P. Jacobsen a,b , J. Gjerstad a,baNational Institute of Occupational Health, Oslo,Norwayb Department of Bioscience, University of Oslo,NorwayE-mail address: Anna.Legfeldt@stami.no (A. Legfeldt).Aims: Lumbar radicular pain is often associated with increasedlocal and systemic synthesis of inﬂammatory mediators. This process can be modulated by speciﬁc microRNAs (miRs). Here, in theanimal model, we investigated the effect of miR-223 on the spinalnociceptive signaling and local gene expression.Methods: In anaesthetized Lewis rats, extracellular single unitrecordings of spinal nociceptive activity and qPCR were used toexplore the effect of miR-223 application onto the dorsal nerveroots (L3–L5).Results: A signiﬁcant decrease in the C-ﬁber response wasobserved following application of miR-223 onto the dorsal nerveroots. In addition, the gene expression of interleukin-6 (IL-6) wasincreased in the spinal cord.Conclusions: Our data suggest that miR-223 may inﬂuencenociceptive signaling in the pain pathways, possibly by modulatingthe expression of inﬂammatory mediators.http://dx.doi.org/10.1016/j.sjpain.2017.04.037177Acute muscle pain alters corticomotor outputof the affected muscle stronger than asynergistic, ipsilateral muscleDennis Boye Larsen a,∗ , Thomas Graven-Nielsen a ,Rogerio Pessoto Hirata b , Shellie A. Boudreau aaCenter for Neuroplasticity and Pain (CNAP), SMI,Department of Health Science and Technology,Aalborg University, Aalborg, Denmarkb SMI, Department of Health Science and Technology,Aalborg University, Aalborg, DenmarkE-mail address: firstname.lastname@example.org (S.A. Boudreau).Aims: Muscle pain affects corticomotor areas representing theaffected muscle, by changing the size of representation and reducesthe corticospinal output as assessed by transcranial magnetic stimulation (TMS). Less work has been done to understand how pain inone muscle group may affect synergistic ipsilateral muscles distalto the pain. This study aimed to explore the effects of acute extensorcarpi radialis (ECR) muscle pain on TMS motor-evoked potentials(MEPs) of the ECR and the ﬁrst dorsal interosseus (FDI) muscle,which are known to strongly overlap within the corticomotor area.Methods: Eight healthy volunteers (1 woman) were injectedwith hypertonic saline (5.8%, 0.5 mL) into the ECR muscle. Painintensity was assessed by the visual analogue scale (VAS) everyminute for 10 min. TMS was applied at 120% of ECR resting motorthreshold, and MEPs were acquired from the ECR and the FDImuscles. At baseline, 10 TMS pulses were delivered. Temporal mapping of ECR and FDI MEPs over 10 min duration was performed bydelivering 100 single-pulses of TMS, at 6 s interstimulus-interval.The MEPs for each muscle were averaged at baseline, peak-pain(1–2 min epoch), and 10 min post-injectionResults: Pain intensity reduced signiﬁcantly at 10 min postinjection as compared to peak-pain (P = 0.011). Further, one-wayrepeated measures analysis of variance revealed that ECR MEPswere altered at peak-pain compared to baseline (P < 0.05), but not10 min post-injection (P > 0.05). Baseline and 10 min post-injectionof ECR MEPs did not differ signiﬁcantly (P = 0.67). The MEPs of theFDI muscle did not show a similar alteration over time (P = 0.1).Conclusions: Despite the overlap between ECR and FDI representations, acute muscle pain of the ECR only signiﬁcantly alteredcortical excitability of the ECR muscle representation.http://dx.doi.org/10.1016/j.sjpain.2017.04.038The subjective sensation induced by variousthermal pulse stimulation in healthy volunteersY. Oono a,∗ , H. Kubo a , T. Imamura a , K.Matsumoto a , S. Uchida a , S. Takagi a , P. Gazerani b ,K. Wang b , L. Arendt-Nielsen b , H. Kohase aaDivision of Dental Anesthesiology, Department ofDiagnostic and Therapeutic Sciences, MeikaiUniversity School of Dentistry, Sakado, Japanb Center for Sensory-Motor Interaction (SMI),Department of Health Science and Technology,Aalborg University, Aalborg, DenmarkE-mail address: email@example.com (Y. Oono).Aims: Novel quantitative thermal stimulator devices (QTSDs)have been developed to deliver thermal pulse stimulation withregulated constant temperatures (0–45 ◦ C) with a Peltier elementprobe (16 cm2 ). The aim of this study was to investigate subjective sensation induced by the interaction between simultaneouslyapplied painful cold and heat stimuli in various sites.Methods: Twenty healthy subjects (12 men and 8 women, agerange: 25–45 years) participated. The intensity of cold pain (CP) and
Scandinavian Journal of Pain – de Gruyter
Published: Jul 1, 2017
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