Pain
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The experience of pain has been documented in small studies of individuals with multiple sclerosis (MS). The present study examines the prevalence of persistent pain and uncomfortable sensations among participants in the large North American Research Committee on MS (NARCOMS) Patient Registry. Registrants (10,176) responded to a questionnaire on pain and 7579 reported experiencing some level of pain during the month prior to the survey. ⋯ About one-third of the patients with moderate pain and 18% of those with severe pain reported no consultations for their pain. The effects of pain severity were fully evident in the respondents' daily life, their work, mood, recreational activities and enjoyment of life. Our results indicate that the high prevalence of MS-related severe pain, low satisfaction with management of intense pain, and the perceived interference with quality of life indicators necessitate greater attention by healthcare providers to the management of pain and uncomfortable sensations in the MS population.
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The contribution of the amygdala to neuropathic pain processing in animals has not been clearly acknowledged. To assess the relative contribution of amygdala GABA-A receptors in mediating sensory-discriminative and affective-motivational pain components, the GABA-A receptor agonist muscimol and the antagonist bicuculline (both 10-25 ng/microl) were administered by acute bilateral injection directly into the central amygdala in rats with a chronic constriction injury (CCI). Escape/avoidance behaviour reflecting the affective-motivational dimension of pain was measured using a light/dark chamber in combination with suprathreshold nociceptive stimulation, and was defined as a shift from the 'non-aversive' dark area of the chamber to the 'aversive' light area. ⋯ Motility behaviour was unaffected by injection of either drug as determined in the open field test. Thus, amygdala GABA-A receptors appear to play an important role in sensory and especially affective pain processing in neuropathic rats. Furthermore, after nerve injury reflex nociceptive behaviours appear to be under tonic control by descending inputs, which originate from or are modulated within the amygdala.