Neuroscience letters
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Neuroscience letters · May 2004
Comparative StudyExpression of calcitonin gene-related peptide type 1 receptor mRNA and their activity-modifying proteins in the rat nucleus accumbens.
The calcitonin receptor-like receptor (CRLR) and the orphan receptor RDC-1 have been proposed to be calcitonin gene-related peptide type 1 (CGRP1) receptors, and receptor activity-modifying proteins (RAMPs) determine the ligand specificity of CRLR. Coexpression of RAMP1 and CRLR resulted in functional CGRP1 receptors; the complex of RAMP2 or RAMP3 and CRLR created functional adrenomedullin receptor. Although high levels of CGRP binding sites in the nucleus accumbens have been reported, little is known about the expression of these novel CGRP receptors. ⋯ Our results demonstrate that CGRP, CRLR, RAMP1 and RAMP2 exist in the nucleus accumbens of intact rats, and that they were significantly upregulated in rats with inflammation. In contrast, no expression was detected for RDC-1 and RAMP3. These findings indicated a functional role for CGRP and its receptors in inflammation and pain modulation.
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Neuroscience letters · May 2004
Peripheral and electrocortical responses to painful and non-painful stimulation in chronic pain patients, tension headache patients and healthy controls.
Sixteen chronic back pain (CBP) patients, 16 tension headache (THA) patients and 16 healthy controls (HC) were exposed to four series of ten electric stimuli at perception threshold, pain threshold and 10% below pain tolerance. The EEG was recorded from three sites, in addition, the EMG from the m. frontalis and m. erector spinae, heart rate and skin conductance were assessed. The CBP patients showed significantly lower pain threshold and pain tolerance values than the HC and the THA patients whereas the THA patients displayed a higher pain tolerance. ⋯ N150, P260, P300 and N500 were not significantly different between the groups nor were there significant group differences in the peripheral measures. However, since the stimulation intensity was significantly lower in the CBP patients, these data are indicative of both enhanced central and peripheral reactivity. The observed lack of habituation may contribute to the persistence of chronic pain.
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Neuroscience letters · May 2004
Peripheral nerve injury evokes disabilities and sensory dysfunction in a subpopulation of rats: a closer model to human chronic neuropathic pain?
Chronic pain conditions for which treatment is sought are characterized usually by complex behavioural disturbances as well as pain. We review here evidence that although chronic constriction injury (CCI) of the sciatic nerve evokes allodynia and hyperalgesia in all rats, persistent social behavioural and sleep disruption occurs only in a subpopulation of animals. ⋯ An absence of correlation between disability and sensory dysfunction is characteristic also of human neuropathic pain. These findings indicate that: (i). in a subpopulation of rats sciatic injury evokes disabilities characteristic of human neuropathic pain conditions; and (ii). testing for sensory dysfunction alone cannot detect this subpopulation.
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Neuroscience letters · May 2004
Cerebellar neural responses related to actively and passively applied noxious thermal stimulation in human subjects: a parametric fMRI study.
Cerebellar activation is consistently found during noxious stimulation but little is known about its pain-related specificity. Under natural circumstances noxious stimuli are actively or passively delivered with concomitant tactile sensory stimulation. ⋯ With respect to psychophysical pain ratings anterior vermal and ipsilateral hemispheric lobule VI activation was parametrically modulated for stimulus intensity in actively but not in passively elicited thermal stimulation. The cerebellum seems to be capable of distinguishing active from passive painful stimuli.
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Acupuncture and electroacupuncture (EA) as complementary and alternative medicine have been accepted worldwide mainly for the treatment of acute and chronic pain. Studies on the mechanisms of action have revealed that endogenous opioid peptides in the central nervous system play an essential role in mediating the analgesic effect of EA. ⋯ A combination of the two frequencies produces a simultaneous release of all four opioid peptides, resulting in a maximal therapeutic effect. This finding has been verified in clinical studies in patients with various kinds of chronic pain including low back pain and diabetic neuropathic pain.