Pain
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Randomized Controlled Trial Clinical Trial
Sensory stimulation (TENS): effects of parameter manipulation on mechanical pain thresholds in healthy human subjects.
Transcutaneous electrical nerve stimulation (TENS) is a popular form of electrostimulation. Despite an extensive research base, there remains no consensus regarding the parameter selection required to achieve maximal hypoalgesic effects. The aim of this double blind, sham-controlled study was to investigate the relative hypoalgesic effects of different TENS parameters (frequency, intensity and stimulation site) upon experimentally induced mechanical pain. ⋯ Whilst high frequency, 'strong but comfortable' intensity, segmental stimulation produced comparable hypoalgesic levels during stimulation, this effect was not sustained post-stimulation. Stimulation at a combination of the two sites did not produce any greater hypoalgesic effects. These results may have implications for the clinical use of sensory stimulation.
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Randomized Controlled Trial Comparative Study Clinical Trial
Postsurgical pain outcome assessment.
Reliable and valid measures of pain are essential for conducting clinical trials of pain treatments. Perhaps the most important aspect of a pain measure's validity is its sensitivity, or ability to detect changes in pain over time and due to treatment. Several factors may affect a measure's sensitivity, including the complexity of the rating task for the measure, the number of pain intensity levels assessed by the measure, the dimension of pain assessed (e.g. pain intensity vs. pain relief), and the number of individual ratings (e.g. single rating vs. composite score) used to create the measure. ⋯ However, contrary to our prediction, a composite measure of outcome made up of all three measures was not consistently superior to the individual measures for detecting treatment effects. Finally, we found that pain relief ratings were related to, but also distinct from, change in pain intensity as measured by changes in pain intensity ratings from baseline to each postmedication assessment point. These findings have important implications for the assessment of pain in clinical trials.
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Comparative Study
Inward currents in primary nociceptive neurons of the rat and pain sensations in humans elicited by infrared diode laser pulses.
Radiant heat is often used to study nociception in vivo. We now used infrared radiation generated by a diode laser stimulator (wavelength 980 nm) to investigate transduction mechanisms for noxious heat stimuli in acutely dissociated dorsal root ganglion (DRG) neurons of rats in vitro. The laser stimulator offered the unique opportunity to test whether the same stimuli also elicit pain sensations in humans. ⋯ No significant differences were seen between the pain thresholds in hairy and in glabrous skin, probably due to the deep penetration of this laser radiation. The mean pain threshold for stimuli > or =200 ms in humans was 2.5 +/- 0.2 J mm(-2) (n = 11), and did not differ from the thresholds for the induction of I(heat) in vitro. Our results indicate that I(heat) in primary sensory neurons can be activated by infrared laser pulses that are painful in humans.
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Facial expression of pain has rarely been researched in the context of facial expression of negative emotions with which it may occur. The main aim of the study was to investigate how pain expression resembled or differed from that of other negative emotions (fear, anger, sadness, surprise, disgust and embarrassment), using multidimensional scaling, a dimensional approach to understanding relationships among emotions. As possible misidentification of facial expressions by participants could distort those results, a judgement study as a categorical approach was conducted to examine the accuracy of identification of pain and negative emotion facial expressions. ⋯ Confidence in ratings approximated accuracy of identification. Multidimensional scaling revealed two dimensions: the first distinguished embarrassment from all other emotion expressions; the second separated pain, sadness and anger from fear, surprise and disgust. Possible explanations for these findings were sought in patterns of facial action units, and in the messages conveyed by the expressions according to Fridlund's Behavioural Ecology View.
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Injury to peripheral dental tissues evokes dynamic alternations in central sensory pathways. We have previously reported that transient stimulation of the dental pulp with noxious heat evokes the induction of the immediate early gene product Fos in the transitional region between subnucleus interpolaris and caudalis (Vi/Vc) and subnucleus caudalis (Vc). A question arises as to whether similar changes occur in response to inflammation to the tooth pulp. ⋯ The number of Fos-positive neurons was greater in the trigeminal subnucleus caudalis (Vc) and the transitional regions (Vi/Vc) in LPS-treated animals compared with sham-operated animals, and greater in the deeper laminae than the superficial laminae of each trigeminal region. LPS treatment did not evoke Fos expression in the rostral trigeminal regions above Vi/Vc. These results demonstrate that LPS-induced pulpal inflammation results in significant alterations in the Vi/Vc and Vc, and such changes may underlie the observed nociceptive behavioral responses and may play an important role in producing a symptomatic pulpitis in humans.