Previous studies by our laboratory established a rat model of neuropathic pain which displayed long-lasting heat hyperalgesia and mechanical allodynia that are sympathetically maintained. The present study was undertaken to extend our earlier findings by examining additional behavioral signs of ongoing pain and cold allodynia in our animal model and testing their sympathetic dependency. Neuropathic surgery was done by tightly ligating the L5 and L6 segmental spinal nerves of rats unilaterally. In addition to the behavioral signs of heat hyperalgesia and mechanical allodynia observed before, these rats displayed signs of ongoing pain (lasting at least 10 weeks) and cold allodynia (lasting at least 16 weeks). These behaviors were reduced markedly after surgical lumbar sympathectomy. The results of the present study, together with the previous study, suggest that our animal model exhibits neuropathic pain behaviors including ongoing pain, heat hyperalgesia, mechanical allodynia and cold allodynia. Since all of these behavioral signs are sympathetically maintained, our model represents a model for sympathetically maintained pain.

This study was conducted to determine the contribution of peripheral inputs from injured and intact afferent fibers to behavioral signs of neuropathic pain, using a previously developed neuropathic rat model. Neuropathic injury was produced by tightly ligating the left L5 and L6 spinal nerves; this procedure induced rats to display neuropathic pain behaviors in the ipsilateral hindlimb. The behaviors included signs of mechanical and cold allodynia, as well as ongoing pain. Five days after neuropathic injury, peripheral inputs from injured segments (L5 and L6) or intact segments (L3 and L4) were blocked by either transection of the dorsal roots or application of a local anesthetic (bupivacaine) to the roots. Dorsal rhizotomy of the injured segments reduced all components of neuropathic pain behaviors. In contrast, dorsal rhizotomy of the uninjured segments abolished behavioral signs of mechanical and cold allodynia, but signs of ongoing pain were preserved. Blocking afferent inputs by application of bupivacaine mimicked the results of dorsal rhizotomy, in a reversible manner. These results suggest that afferent signals from injured and intact fibers play distinctively different roles in neuropathic pain: inputs from injured afferents maintain all components of neuropathic pain, while those from intact afferents mediate evoked pain such as mechanical and cold allodynia. An hypothesis is proposed to explain the results of the present as well as other published studies.

This study investigated the short-term effects of Kinesio taping (KT) on various types of pain, active range of motion (AROM), and proprioception in patients with knee osteoarthritis. Forty-six older participants (mean [SD], 57.9 [4.4] yrs) with osteoarthritis were randomly allocated to two groups: the KT group or the placebo-KT group. Taping with tension (KT application) or without tension (placebo-KT application) was applied to the quadriceps of the participants in both groups. Before and after intervention, pain intensity was measured using a visual analog scale at rest and during walking, and pressure pain thresholds (PPTs) were assessed using an algometer in the quadriceps and the tibialis anterior. In addition, pain-free AROM and proprioception were measured. The KT group showed attenuation of pain during walking (effect size [ES], 1.97), PPT in the quadriceps (ES, 2.58), and PPT in the tibialis anterior (ES, 2.45). This group also showed significantly improved AROM (ES, 2.01) and proprioception (ES, 1.73-1.89; P < 0.05). However, the placebo-KT group did not show significant changes in pain, AROM, or proprioception. There were significant differences between the two groups in pain during walking and PPT. In addition, pain during walking showed a significant correlation with AROM and proprioception, and a significant correlation was found between PPT and AROM. These results demonstrated that KT application with proper tension to the quadriceps effectively attenuates various types of pain and improves AROM and proprioception in osteoarthritis patients. Thus, KT may be a suitable intervention to improve pain, AROM, and proprioception in patients with osteoarthritis in clinics.