Articles: hyperalgesia.
-
Mechanical dynamic allodynia is a hallmark symptom of postherpetic neuralgia, but the mechanisms are unclear. This study examined the participation of injury to sensory C-fiber and A-fiber neurons in postherpetic dynamic allodynia. Percutaneous inoculation of mice with herpes simplex virus type-1 caused zoster-like skin lesions and dynamic allodynia, which persisted after lesion healed. ⋯ Calcitonin gene-related peptide immunoreactivity (a C-fiber marker) was markedly reduced, but neurofilament 200 immunoreactivity (an A-fiber neuron marker) was unchanged in the scarred skin of postherpetic mice. In the affected dorsal root ganglion of postherpetic mice, peripherin-immunoreactive (a C-fiber neuron marker) neurons reduced significantly, whereas neurofilament 200-immunoreactive neurons did not. These results suggest that postherpetic dynamic allodynia is associated with injury to sensory C-fiber neurons and little damage to A-fiber neurons.
-
Neuroscience letters · Feb 2013
The effects of menthol on cold allodynia and wind-up-like pain in upper limb amputees with different levels of phantom limb pain.
The mechanisms underlying phantom limb pain are not fully known, but hypersensitivity appears to be a central element. Menthol has previously been suggested as a model for hypersensitivity, but it has not yet been investigated if different levels of neuropathic pain may influence the effects of menthol or if topical application of menthol may act as a model for hypersensitivity in patients with phantom limb pain. In the present study, menthol (l-menthol 40%) was applied to the affected and non-affected sides in 24 upper-limb amputees with different levels of phantom limb pain to test if menthol could induce cold allodynia and exacerbate wind-up-like pain. ⋯ After application of menthol, the level of phantom limb pain was only related to wind-up-like pain following brush (P=0.011) but not pinprick stimulation (P=0.233). This study indicates that menthol does influence hypersensitivity in phantom limb pain patients, and it is the first study to show that menthol may exacerbate wind-up-like pain in this group of neuropathic pain patients. The findings suggest that menthol may act as a model for studying sensitization in phantom limb patients.
-
Neuroscience letters · Feb 2013
Treadmill running and static stretching improve long-lasting hyperalgesia, joint limitation, and muscle atrophy induced by cast immobilization in rats.
The effects of exercise on chronic pain induced by immobilization are incompletely understood. The purpose of this study was to investigate whether 30min of treadmill running (TR; active exercise) and 10min of static stretching (SS; passive exercise) of the immobilized hindlimb reduce widespread chronic pain, joint limitation, and hindlimb muscle atrophy induced by cast immobilization in rats. One hindlimb of Sprague Dawley (SD) rats was immobilized for 2 weeks with a cast, and remobilization was conducted for 7 weeks. ⋯ Both forms of exercise significantly inhibited mechanical hyperalgesia in the calf and hindpaw in immobilized rats. Range-of-motion limitations in the knee and ankle joints and calf muscle atrophy after cast removal were also decreased by both TR and SS. This study is the first to demonstrate the beneficial effect of TR and SS on widespread chronic pain, joint limitation, and muscle atrophy in a cast-immobilized rat model.
-
Clinical Trial
Assessment of pressure-pain thresholds and central sensitization of pain in lateral epicondylalgia.
OBJECTIVE.: To assess pain sensitivity and spreading hyperalgesia in lateral epicondylalgia (LE). SUBJECTS.: Twenty-two women with LE, and 38 controls were included. OUTCOME MEASURES.: Computerized cuff pressure algometry was used for assessment of pressure-pain threshold and tolerance. ⋯ In LE patients without signs of peripheral inflammation assessed by Doppler ultrasound, temporal summation was significantly stronger than in patients with ongoing inflammation (P < 0.01). CONCLUSION.: Patients with LE may be subgrouped based on pain hypersensitivity and Doppler ultrasound into clinically meaningful subgroups with varying duration of symptoms and different degrees of central sensitization. These groups may require different pain management strategies.
-
We aim to determine the effects of botulinum toxin type A (BTX-A) on the thresholds of pain and the expression of transient receptor potential vanilloid type 1 (TRPV1) in the dorsal root ganglion (DRG) in rats with neuropathic pain induced by selective ventral root transection (VRT). ⋯ Upregulation of TRPV1 expression in the DRG is an important mechanism of neuropathic pain induced by the VRT. The analgesic effect of BTX-A is most likely mediated through reduction of TRPV1 expression in the nociceptors.