Pain
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Comparative Study
In vivo recruitment by painful stimuli of AMPA receptor subunits to the plasma membrane of spinal cord neurons.
The persistent increase in pain sensitivity observed after injury, known as hyperalgesia, depends on synaptic plasticity in the pain pathway, particularly in the spinal cord. Several potential mechanisms have been proposed, including post-synaptic exocytosis of the AMPA subclass of glutamate receptors (AMPA-R), which is known to play a critical role in synaptic plasticity in the hippocampus. AMPA-R trafficking has been described in spinal neurons in culture but it is unknown if it can also occur in spinal neurons in vivo, or if it can be induced by natural painful stimulation. ⋯ Brefeldin-A, an antibiotic that inhibits exocytosis of proteins, not only prevented GluR1 trafficking to the membrane but also inhibited referred hyperalgesia in capsaicin-treated mice. Our results show that delivery of GluR1 AMPA receptor subunits to the cell membrane through a CaMKII activity-dependent exocytotic regulated pathway contributes to the development of hyperalgesia after a painful stimulus. We conclude that AMPA-R trafficking contributes to the synaptic strengthening induced in the pain pathway by natural stimulation.
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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.
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Comparative Study
Chronic orofacial pain among Korean elders: prevalence, and impact using the graded chronic pain scale.
The aims of this study were to investigate the prevalence of orofacial pain symptoms in the Korean elderly population, and to evaluate factors associated with orofacial pain and graded chronic pain. Of 4,342 Korean elders from the cohort of Korean National Interview Survey of Oral Health Status in 2000, telephone interviews were conducted on a stratified random sample of 1,032 people aged 55 years or older. Prevalence of five orofacial pain symptoms (jaw joint pain, face pain, toothache, oral sores, and burning mouth) in the past 6 months along with questions from the graded chronic pain scale were assessed by telephone using a structured questionnaire. ⋯ Subjects with joint pain, burning mouth or toothache pain were more likely to report high levels of a pain-related disability compared with subjects not reporting those symptoms. There were no age group differences in pain intensity, but the older age group reported a higher number of disability days because of their pain. Chronic orofacial pain is a substantial health problem in the elderly population.
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Comparative Study
Gender differences in patient-spouse interactions: a sequential analysis of behavioral interactions in patients having osteoarthritic knee pain.
Theory and research suggest that spousal responses to displays of pain behavior can vary markedly. To our knowledge, observational research on spousal responses to pain behavior has been carried out only in chronic low back pain patients, but not in other populations. In this study systematic observations were conducted of interactions occurring between 50 married osteoarthritis patients (25 male and 25 female) and their respective spouses. ⋯ Contrary to prior research on chronic low back pain this study found that in osteoarthritis patients spouse facilitative behavior preceded and followed patient pain behavior significantly more often than did spouse solicitous behavior. A gender difference in spousal responding to pain behavior also was observed in that wives were significantly more likely to show facilitative behavior preceding and following patient pain behavior than were husbands. The implications of these findings for future research and clinical interventions focused on patient-spouse interactions are discussed.