Pain
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Microglial cells, the resident immune cells of the spinal cord, become activated in response to peripheral nerve injury. Microglia activation contributes to the development of neuropathic pain. Here we employed microarray analysis of individually collected pools of 10 spinal microglia cells to identify changes of levels and cell-to-cell expression variance of microglial genes during their activation after peripheral nerve injury. ⋯ Early POD1 microglia exhibited a very distinct expression profile compared to late POD7 microglia, possibly leading to the transition from initiation to maintenance of neuropathic pain. We found sample variance patterns that were consistent with the hypothesis that microglia were highly heterogeneous at the level of individual cells, and variation analysis identified 56 microglial genes potentially linked to the maintenance of neuropathic pain which included Gria1. This study provides insights into spinal microglial biology and reveals novel microglial targets for the treatment of neuropathic pain.
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The purposes of this study, in oncology outpatients receiving chemotherapy (n = 926), were to: describe the occurrence of different types of pain (ie, no pain, only noncancer pain [NCP], only cancer pain [CP], or both CP and NCP) and evaluate for differences in demographic, clinical, and symptom characteristics, and quality of life (QOL) among the 4 groups. Patients completed self-report questionnaires on demographic and symptom characteristics and QOL. Patients who had pain were asked to indicate if it was or was not related to their cancer or its treatment. ⋯ The most common comorbidities in the NCP group were back pain, hypertension, osteoarthritis, and depression. Unrelieved CP and NCP continue to be significant problems. Oncology outpatients need to be assessed for both CP and NCP conditions.
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Editorial Comment
The interpersonal function of pain: Conserving multiple resources.
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High-frequency spontaneous firing in myelinated sensory neurons plays a key role in initiating pain behaviors in several different models, including the radicular pain model in which the rat lumbar dorsal root ganglia (DRG) are locally inflamed. The sodium channel isoform NaV1.6 contributes to pain behaviors and spontaneous activity in this model. Among all isoforms in adult DRG, NaV1.6 is the main carrier of tetrodotoxin-sensitive resurgent Na currents that allow high-frequency firing. ⋯ NaVβ4 siRNA also reduced immunohistochemical NaV1.6 expression. Patch-clamp recordings of tetrodotoxin-sensitive Na currents in acutely cultured medium diameter DRG neurons showed that DRG inflammation increased transient and especially resurgent current, effects blocked by NaVβ4 siRNA. NaVβ4 may represent a more specific target for pain conditions that depend on myelinated neurons expressing NaV1.6.