Pain
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Patients with Parkinson's disease (PD) reportedly show deficits in sensory processing in addition to motor symptoms. However, little is known about the effects of bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) on temperature sensation as measured by quantitative sensory testing (QST). This study was designed to quantitatively evaluate the effects of STN-DBS on temperature sensation and pain in PD patients. ⋯ The CPTs and HPTs in PD patients were significantly larger on the more affected side than on the less affected side (P<.02). Because elevations in thermal sense and pain thresholds of QST are reportedly almost compatible with decreases in sensation, our findings confirm that temperature sensations may be disturbed in PD patients when compared with healthy persons and that STN-DBS can be used to improve temperature sensation in these patients. The mechanisms underlying our findings are not well understood, but improvement in temperature sensation appears to be a sign of modulation of disease-related brain network abnormalities.
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Peripheral inflammation alters AMPA receptor (AMPAR) subunit trafficking and increases AMPAR Ca(2+) permeability at synapses of spinal dorsal horn neurons. However, it is unclear whether AMPAR trafficking at extrasynaptic sites of these neurons also changes under persistent inflammatory pain conditions. Using patch-clamp recording combined with Ca(2+) imaging and cobalt staining, we found that, under normal conditions, an extrasynaptic pool of AMPARs in rat substantia gelatinosa (SG) neurons of spinal dorsal horn predominantly consists of GluR2-containing Ca(2+)-impermeable receptors. ⋯ This increase was also accompanied by an inward rectification of AMPA-induced currents and enhancement of sensitivity to a highly selective Ca(2+)-permeable AMPAR blocker, IEM-1460. Electron microcopy and biochemical assays additionally showed an increase in the amount of GluR1 at extrasynaptic membranes in dorsal horn neurons 24h post-CFA. Taken together, our findings indicate that CFA-induced inflammation increases functional expression and proportion of extrasynaptic GluR1-containing Ca(2+)-permeable AMPARs in tonically firing excitatory dorsal horn neurons, suggesting that the altered extrasynaptic AMPAR trafficking might participate in the maintenance of persistent inflammatory pain.
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Editorial Comment Review
Acupuncture's claims punctured: not proven effective for pain, not harmless.
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Idiopathic or functional abdominal pain (FAP) is common in school-age children and typically reflects a functional gastrointestinal disorder (FGID). FGIDs in adults have been distinguished by enhanced responses of the central nervous system to pain stimuli, known as central sensitization. This study investigated whether adolescents and young adults with a history of pediatric FAP (n=144), compared with well control subjects (n=78), showed enhanced central sensitization demonstrated by greater temporal summation (wind-up) to brief, repetitive heat pulses. ⋯ Although anxiety was significantly higher in the FAP group compared with control subjects (P<.01) and in women compared with men (P<.05), anxiety did not explain the increased wind-up observed in women with a childhood history of FAP. Results suggest that women with a pediatric history of FAP may have a long-term vulnerability to pain associated with enhanced central nervous system responses to pain stimuli. Young women with a childhood history of functional abdominal pain may have a long-term vulnerability to pain that is associated with enhanced responses of the central nervous system to pain stimuli.
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Pain catastrophizing is associated with enhanced temporal summation of pain (TS-Pain). However, because prior studies have found that pain catastrophizing is not associated with a measure of spinal nociception (nociceptive flexion reflex [NFR] threshold), this association may not result from changes in spinal nociceptive processes. The goal of the present study in healthy participants was to examine the relationship between trait (traditional) and state (situation-specific) pain catastrophizing and temporal summation of NFR (TS-NFR) and TS-Pain. ⋯ Trait catastrophizing was not related to TS-Pain or TS-NFR. Together, these results confirm prior studies that indicate that catastrophizing enhances pain via supraspinal processes rather than spinal processes. Moreover, because catastrophizing was associated with TS-Pain but not TS-NFR, caution is warranted when using pain ratings to infer temporal summation of spinal nociceptive processes.