Pain
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Comparative Study
Social networks and pain interference with daily activities in middle and old age.
Social networks have emerged as important in the development and progression of disability in aging cohorts. We have previously reported that pain that interferes with daily activities is common and increases incrementally from middle age into later life. The current study has investigated whether pain interference in this age group is related to social network characteristics. 5215 community-dwelling adults aged 50 years and over participating in the North Staffordshire Osteoarthritis Project (NorStOP) and identified as currently experiencing pain formed the sample for the present analysis. ⋯ The associations with close friends and children were reduced but remained significant after adjusting for sociodemographic factors. The association with close friends became non-significant after adjusting for depression suggesting this may form part of the pathway linking close friends networks and pain interference. Pain-related interference shows similar associations with social networks as all-cause disability and may benefit similarly from a public health perspective.
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Comparative Study
The effects of acute and chronic restraint stress on activation of ERK in the rostral ventromedial medulla and locus coeruleus.
Extracellular signal-regulated kinase (ERK) is a key molecule in numerous cellular and physiological processes in the CNS. Exposure to stressors causes substantial effects on the perception and response to pain. The rostral ventromedial medulla (RVM) and the locus coeruleus (LC) play crucial roles in descending pain modulation system. ⋯ Protein levels of tryptophan hydroxylase were significantly increased in the RVM region in the 3-week restraint rats. On the other hand, the chronic restraint stress significantly decreased p-ERK-IR in the LC [P<0.05]. These findings suggest that chronic restraint stress-induced activation of ERK in the RVM and the suppression in the LC may be involved in the modulation of the pain threshold by chronic stress.
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Comparative Study
Spontaneous discharge and increased heat sensitivity of rat C-fiber nociceptors are present in vitro after plantar incision.
Postoperative pain is characterized by spontaneous pain at the surgical site and increased pain due to movements. To study postoperative pain mechanisms, we investigated discharge properties of mechano-heat sensitive C-fiber afferents innervating the rat glabrous hindpaw skin 1 day after plantar incision. Behaviors indicating spontaneous pain, heat and mechanical hyperalgesia were present 1 day after incision. ⋯ The mean mechanical response thresholds, measured by a servo force-controlled stimulator, were not different between groups. The total spikes evoked at supra-threshold mechanical stimulation were not increased in afferents from the incision. In conclusion, 1 day after incision, when behaviors indicating spontaneous pain, heat and mechanical hyperalgesia are present, C-fibers close to incision showed spontaneous discharge and sensitization to heat but not to mechanical stimuli, in vitro.
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Comparative Study
Refractoriness cannot explain why C-fiber laser-evoked brain potentials are recorded only if concomitant Adelta-fiber activation is avoided.
Co-activation of Adelta- and C-fiber nociceptors by brief cutaneous laser heat stimuli may induce a dual sensation composed of first and second pain but evokes only a single, Adelta-fiber related, late laser-evoked potential (LEP). Yet, when concomitant activation of Adelta-nociceptors is avoided, C-nociceptor activation evokes an ultra-late LEP. As cumulating evidence indicates that late and ultra-late LEPs may share common generators, investigators have hypothesized that when Adelta-fibers trigger a late LEP, the later arriving C-fiber afferent volley cannot trigger an ultra-late LEP because underlying generators are in a 'refractory state'. ⋯ Studies have shown that this component is probably related to the P3b component described in other sensory modalities. This result provides support to the 'context closure' model hypothesizing that this component reflects the closure of information processing occurring when expectations are terminated. Altogether, these results suggest that late and ultra-late LEPs reflect very general processes, which are mainly related to detection and orientation and constitute only a fraction of the central processing of both nociceptive inputs.
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The present study investigated the effects of two attributes of the experimenter (gender and professional status) on the report and tolerance of pain in male and female subjects. 160 non-psychology students (80 male and 80 female, aged 17-59 years) participated in a cold-pressor task. Subjects were assigned to one of 8 groups: male (M) and female (F) experimenters tested male (m) and female (f) students. In each combination (Mm, Mf, Fm, Ff), the cold-pressor task was conducted by either one of two faculty members (high professional) or one of two students (low professional). ⋯ Further, a significant interaction of experimenter gender and subject gender on pain tolerance indicated that subjects also tolerated pain longer when they were tested by an experimenter of the opposite sex. Additionally, a significant main effect for experimenter gender showed higher pain intensities for subjects tested by female experimenters. The observation that pain responsivity is influenced by the professional status of the experimenter might have implications for the study of pain in general and should be addressed in more detail in future experiments.