Pain
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Although dealing with pain is a vital goal to pursue, most individuals are also engaged in the pursuit of other goals. The aim of the present experiment was to investigate whether attentional bias to pain signals is inhibited when one is pursuing a concurrent salient but nonpain task goal. Attentional bias to pain signals was measured in pain-free volunteers (n=63) using a spatial cueing task with pain cues and neutral cues. ⋯ As predicted, the results show attentional bias to pain signals in the control group, but not in the goal group. This indicates that attentional bias to signals of impending pain is inhibited when one is engaged in the pursuit of another salient but nonpain goal. The results of this study underscore a motivational view on attention to pain, in which the pursuit of multiple goals, including nonpain goals, is taken into account.
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Comparative Study
How efficient is the orienting of spatial attention to pain? An experimental investigation.
This study investigated how efficient spatial attention was oriented to pain in 2 experiments. Participants detected whether painful (pain group) or nonpainful (control group) somatosensory stimuli were delivered to the left or right hand. Each stimulus was preceded by a visual cue presented near to the stimulated hand (valid trial), the opposite hand (invalid trial), or centrally between hands. ⋯ This effect was due to faster responses on valid relative to baseline trials (engagement), rather than slower responses on invalid relative to baseline trials (disengagement), and was significantly correlated with self-reported bodily threat. In experiment 2, prioritization of the pain location was probably overridden by task strategies because it was advantageous for participants' task performance to attend to the cued location irrespective of whether stimulation was painful or not. Implications of these findings for theories of hypervigilance and attentional management of pain are discussed.
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Accumulated evidence suggests that the C-C motif chemokine ligand 5 (CCL5) modulates migration of inflammatory cells in several pathological conditions. This study tested the hypothesis that lack of CCL5 would modulate the recruitment of inflammatory cells to painful, inflamed sites and could attenuate pain in a murine chronic neuropathic pain model. Nociceptive sensitization, immune cell infiltration, multiple cytokine expression, and opioid peptide expression in damaged nerves were studied in wild-type (CCL5 +/+) and CCL5-deficient (CCL5 -/-) mice after partial sciatic nerve ligation (PSNL). ⋯ We demonstrated that lack of CCL5 modulated cell infiltration and the proinflammatory milieu within the injured nerve. Attenuated behavioral hypersensitivity in CCL5 -/- mice observed in the current study could be a result of decreased macrophage infiltration, mobilization, and functional ability at injured sites. Collectively, the present study results suggest that CCL5 receptor antagonists may ultimately provide a novel class of analgesics for therapeutic intervention in chronic neuropathic pain.
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Damage to peripheral nerves causes significant remodeling of peripheral innervation and can lead to neuropathic pain. Most nociceptive primary afferents are unmyelinated (C fibers) and subdivided into peptidergic and nonpeptidergic fibers. Previous studies have found nerve injury in the trigeminal system to induce changes in small-diameter primary afferent innervation and cause significant autonomic sprouting into the upper dermis of the lower-lip skin of the rat. ⋯ These changes were associated with significant increase in glial-derived nerve growth factor levels in the lower-lip skin. While IB4-saporin treatment had no effect on evoked mechanical thresholds when von Frey hairs were applied to the lower-lip skin, ablation of nonpeptidergic fibers in a chronic constriction injury model caused significant sympathetic and parasympathetic fiber sprouting, and led to an exacerbated pain response. This was an unexpected finding, as it has been suggested that nonpeptidergic fibers play a major role in mechanical pain, and suggests that these fibers play a complex role in the development of neuropathic pain.