The journal of pain : official journal of the American Pain Society
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The Acquisition and Extinction of Fear of Painful Touch: a Novel Tactile Fear Conditioning Paradigm.
Fear of touch, due to allodynia and spontaneous pain, is not well understood. Experimental methods to advance this topic are lacking, and therefore we propose a novel tactile conditioning paradigm. Seventy-six pain-free participants underwent acquisition in a predictable as well as an unpredictable pain context. ⋯ Cue exposure reduced fear of touch, whereas context exposure reduced contextual fear. Thus, painful touch leads to increased fear, as does touch in the same context as unpredictable pain, and extinction protocols can reduce this fear. We conclude that tactile conditioning is valuable for investigating fear of touch and can advance our understanding of chronic pain.
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Chronic pain is a common condition associated with psychological distress, functional impairments, and age-associated comorbidity. Preliminary studies, on the basis of relatively small sample sizes, suggest that the combination of chronic pain and stress is associated with telomere shortening, a widely recognized marker of cellular aging. We sought to determine the cross-sectional association of chronic pain with telomere length in 7,816 community-dwelling adults ages 20 years and older who participated in the 1999 to 2002 National Health and Nutrition Examination Survey. ⋯ The age-adjusted means (standard error) of telomere length telomere to single copy gene ratios were 1.04 (.02), 1.03 (.02), and 1.02 (.02) in participants with no chronic pain, chronic regional pain, and chronic widespread pain, respectively (P = .69). In addition, chronic pain did not modify the effects of age, sex, race/ethnicity, education, or psychological distress on telomere length. In summary, chronic regional and widespread pain were not associated with telomere length in this nationally representative study; however, we could not determine associations of pain duration and severity with telomere length because of limitations in pain assessment data.
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Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation. There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch and pain. ⋯ Itch was significantly reduced (conditioned itch modulation-effect) by contra- as well as ipsilateral applied conditioning pain (both P < .001), whereas conditioning itch stimulation only marginally reduced itch. Endogenous descending itch inhibition through mechanisms that are independent of segmental gating can be readily evoked by heterotopic conditioning pain stimulation. However, robust descending inhibition of itch cannot be evoked with conditioning itch stimulation.