Pain
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Pain can be endogenously modulated by heterotopic noxious conditioning stimulation (HNCS) through a mechanism which is known as diffuse noxious inhibitory control (DNIC). Since DNIC can be impaired in patients suffering from chronic pain, a comparable impaired itch inhibition may exist in patients suffering from chronic itch. The aim of the present study was to investigate whether heterotopic pruritic conditioning stimulation (HPCS) would display an impaired modulation of itch in patients suffering from chronic itch compared with healthy subjects. ⋯ As expected, the intensity of itch evoked by the electrical stimulus was significantly less after than before HPCS in healthy subjects, and the same was found for the intensity of electrically evoked pain after compared to before HNCS. Contrarily, in the patients levels of electrically evoked itch were significantly higher after than before HPCS, and no significant difference in pain intensity before and after HNCS was observed. In line with pain modulation, results suggest that there is a DNIC analogous mechanism for itch, i.e., diffuse pruritic inhibitory control (DPIC), which is impaired in patients with chronic itch, possibly due to a dysregulation of descending itch modulatory systems.
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Behavioral analgesic techniques such as distraction reduce pain in both clinical and experimental settings. Individuals differ in the magnitude of distraction-induced analgesia, and additional study is needed to identify the factors that influence the pain relieving effects of distraction. Catastrophizing, a set of negative emotional and cognitive processes, is widely recognized to be associated with increased reports of pain. ⋯ In addition, high catastrophizers rated pain significantly higher regardless of whether the subjects were distracted. Catastrophizing did not influence the overall degree of distraction analgesia; however, early in the session high catastrophizers had little distraction analgesia, though later in the session low and high catastrophizers rated pain similarly. These results suggest that both distraction and catastrophizing have substantial effects on experimental pain in normal subjects and these variables interact as a function of time.
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Research indicates pain may be influenced by the menstrual cycle. While the mechanisms underlying these effects are unclear, it is possible that menstrual phase-related changes in endogenous pain modulation contribute. The present study used well-validated methods to study affective modulation of pain and the nociceptive flexion reflex (NFR) in healthy women during two menstrual phases (mid-follicular vs. late-luteal). ⋯ These modulatory effects were similar in both menstrual phases. Together, these findings suggest that affective engagement of corticospinal mechanisms does not differ across these phases of the menstrual cycle. However, future research is needed to directly assess the relationship between affective modulation of pain/nociception and inter- and intra-individual differences in ovarian hormones and to extend these findings to women who suffer from menstrual cycle-related pain (e.g., premenstrual dysphoric disorder, fibromyalgia).
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The ethics of placebo research have been of paramount concern since the discovery of the phenomenon. To address these ethical concerns, Miller and colleagues (PLoS Med 2005 Sep;2(9):e262, 0853-0859) propose an alternate approach to placebo research, called "authorized deception", in which participants are alerted of the use of deception in the research prior to study enrollment and thus knowingly permit its use if they decide to participate. The present study sought to investigate the authorized deception methodology in experimentally induced placebo analgesia. ⋯ The majority of participants who received this form of consent preferred it to the traditional approach in which the participants are not alerted to the presence of deception. These findings suggest that the use of authorized deception is a viable and ethically preferable alternative consent process for laboratory-based studies on placebo analgesia. Further studies are needed to examine the effect of authorized deception in clinical trials and other placebo research within a clinical setting.