Pain
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Many chronic pain conditions including complex regional pain syndrome are exacerbated by sympathetic activity. In animal models, sympathetic fibers sprout into the dorsal root ganglia (DRG) after peripheral nerve injury, forming abnormal connections with sensory neurons. However, functional studies of sympathetic-sensory connections have been limited largely to in vivo studies. ⋯ In whole DRG isolated 3 days after SNL, microelectrode recordings of sensory neurons showed that repeated stimulation of the dorsal ramus enhanced spontaneous activity in large and medium diameter neurons and reduced rheobase in large neurons. These effects, which were slow and long lasting, were attributed to stimulation of the sympathetic sprouts because: stimulation had no effect in uninjured DRG; and effects could be reduced or eliminated by a "cocktail" of antagonists of norepinephrine and ATP receptors, by pretreatment with the sympathetic release blocker bretylium, or by pre-cutting the grey ramus through which sympathetic fibers coursed to the ligated DRG. The latter treatment, a relatively minimal form of sympathectomy, was also highly effective in reducing mechanical pain ipsilateral to the SNL.
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Rheumatoid arthritis (RA) is a chronic autoimmune arthritis that affects approximately 1% of the population. Synovial inflammation cannot fully explain the level of pain reported by patients and facilitation of pain processing at the spinal level has been implicated. We characterized the K/BxN serum transfer arthritis model as a model of joint inflammation-induced pain and examined pharmacologic responsiveness and spinal glia activation. ⋯ ATF3, a marker of nerve injury, was significantly increased in the lumbar dorsal root ganglia during the late phase (day 28). Hence, serum transfer in the K/BxN serum transfer arthritis model produces a persistent pain state, where the allodynia during the inflammatory state is attenuated by TNF and prostaglandin inhibitors, and the pharmacology and histochemistry data suggest a transition from an inflammatory state to a state that resembles a neuropathic condition over time. Therefore, the K/BxN serum transfer model represents a multifaceted model for studies exploring pain mechanisms in conditions of joint inflammation and may serve as a platform for exploring novel treatment strategies for pain in human arthritic conditions.
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Brief noxious heat evokes more intense pain in women than in men; however, sex differences in the intensity of pain sensations evoked in hairy and glabrous skins are not clearly understood. Glabrous skin putatively lacks the type of A-delta nociceptors that underlie heat-evoked sharp sensation. Therefore, we assessed whether noxious heat-evoked pain qualities differed for hairy and glabrous skins and whether sex differences exist in these evoked pains. ⋯ Sharp, stinging and cutting sensations were evoked in glabrous skin, but the magnitude of these sensations was greater in hairy skin than glabrous skin; an effect only in females. Also, there was no sex difference in sharp sensation and annoyance in glabrous skin. These findings suggest that sharp sensations are evoked more prominently in hairy than in glabrous skin of women and that sharp sensations and annoyance play a prominent role in mediating aspects of pain-evoked from hairy skin in women.
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Randomized Controlled Trial Multicenter Study
Prevention of medication overuse in patients with migraine.
This multi-center study compared the therapeutic effect of a cognitive-behavioral minimal contact program (MCT) to the effect of a brochure (bibliotherapy) for the prevention of medication overuse headache (MOH) in migraine patients. Seven German headache centers recruited 182 migraine patients with high triptan or analgesic intake frequency. Patients were randomly allocated to either the MCT-group, receiving both an MCT program and an educational brochure or to the biblio-group receiving only the brochure. ⋯ Psychological improvements remained stable in both groups at short- and long-term follow-up. During the study, none of the patients developed an MOH. MCT- and bibliotherapy are useful in migraine patients to prevent medication overuse headache or the transition of episodic to chronic headache.
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The primary purpose of the present study was to examine the temporal stability of communicative and protective pain behaviors in patients with chronic back pain. The study also examined whether the stability of pain behaviors could be accounted for by patients' levels of pain severity, catastrophizing, or fear of movement. Patients (n=70) were filmed on two separate occasions (i.e., baseline, follow-up) while performing a standardized lifting task designed to elicit pain behaviors. ⋯ Regression analyses also showed that pain behaviors remained stable when accounting for patients' levels of catastrophizing and fear of movement. Discussion addresses the potential contribution of central neural mechanisms and social environmental reinforcement contingencies to the stability of pain behaviors. The discussion also addresses how treatment interventions specifically aimed at targeting pain behaviors might help to augment the overall impact of pain and disability management programs.