Pain
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This study examined the influence of patients' likability on pain estimations made by observers. Patients' likability was manipulated by means of an evaluative conditioning procedure: pictures of patients were combined with either positive, neutral, or negative personal traits. Next, videos of the patients were presented to 40 observers who rated the pain. ⋯ The effect on pain estimations was only found with regard to patients expressing high-intensity pain. There was no effect on response bias (i.e., the overall tendency to indicate pain). These findings suggest that we take the pain of patients we do not like less seriously than the pain of patients we like.
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Comparative Study
Genotype-selective phenotypic switch in primary afferent neurons contributes to neuropathic pain.
Pain is normally mediated by nociceptive Aδ and C fibers, while Aβ fibers signal touch. However, after nerve injury, Aβ fibers may signal pain. Using a genetic model, we tested the hypothesis that phenotypic switching in neurotransmitters expressed by Aβ afferents might account for heritable differences in neuropathic pain behavior. ⋯ Substance P immunoreactivity was also upregulated in large-diameter neurons, but this change was similar in the 2 lines. Our findings suggest that phenotypic switching contributes to the heritable difference in pain behavior in HA vs LA rats. Specifically, we propose that in HA rats, but less so in LA rats, injured, spontaneously active Aβ afferents both directly drive CGRP-sensitive central nervous system pain-signaling neurons and also trigger and maintain central sensitization, hence generating spontaneous pain and tactile allodynia.
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Brainstem and spinal mechanisms mediating visceral nociception are investigated here using electrophysiology and immunohistochemistry techniques in a model of acute visceral pain. Colorectal distension (CRD) produced graded visceromotor responses (VMR) in normal rats, and these were facilitated by intracolonic mustard oil (MO) that generated acute visceral hyperalgesia. The neuropathic pain drug pregabalin (PGB) is thought to have state-dependent effects in attenuating neuropathic, but not acute somatic pain, likely by impairing calcium-channel trafficking. ⋯ The effects of CRD on RVM cells classed as ON, OFF, or NEUTRAL were independent of their somatic responses, with surprising changes in RVM cell activity to innocuous visceral stimulation. PGB also markedly reduced the visceral responses of RVM ON-cells to noxious CRD. These results illustrate clear differences in the central processing of visceral and somatic stimuli, yet a common role for descending modulation by brainstem activity in mediating evoked pain measures.
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Comparative Study
Chronic idiopathic pain in adolescence--high prevalence and disability: the young HUNT Study 2008.
The aim of this study was to determine the prevalence of self-reported chronic idiopathic pain among adolescents in relation to age and gender, and to explore how pain interferes with daily activities. The study was performed in Nord-Trøndelag County, Norway in 2006-2008. All adolescents were invited to participate; the response rate was 78%. ⋯ A high number of pain-associated disabilities were reported, and 58.5% described difficulties doing daily activities in leisure time. Subjective disabilities were higher in girls, and increased with the frequency of pain and the number of pain locations, as shown by high disability in adolescents with musculoskeletal pain in 3 or more locations. Chronic idiopathic pain, especially multisite pain, is common among adolescents, and those suffering from it report a major impact on several areas of daily living.
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Pain and focal dystonias have been associated with chronic pain conditions such as complex regional pain syndrome. Corneal pain, frequently known as "dry eye", may be a neuropathic pain condition with abnormalities of the nerve plexus. Here we present 5 case histories of patients with defined corneal pain (with associated neuropathic features) and objective measures of changes in the nerve plexus and associated blepharospasm. A putative relationship between pain and blepharospasm suggests potential involvement of the basal ganglia in both these conditions.