Neuroscience letters
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Neuroscience letters · Aug 2002
Involvement of adenosine in the anti-allodynic effect of amitriptyline in streptozotocin-induced diabetic rats.
Recent observations suggest the involvement of adenosine in the peripheral antinociceptive effect of amitriptyline in nerve-injury-induced neuropathic pain. The aim of the present investigation was to evaluate, firstly, the peripheral and systemic effects of amitriptyline on tactile allodynia in the streptozotocin (STZ)-induced diabetic rat model of neuropathic pain and, secondly, whether caffeine coadministration affects the actions of amitriptyline. Diabetes was induced by a single intraperitoneal (i.p.) injection of STZ (50 mg/kg), and tactile allodynia was detected by application of von Frey filaments to the ventral surface of the hindpaw. ⋯ Coadministration of caffeine (5 mg/kg, i.p.; 1500 nmol, s.c.), at doses which produced no effect on its own, partially reversed systemic and local anti-allodynic effects of amitriptyline. These results indicate an anti-allodynic effect of both peripheral and systemic amitriptyline, and suggest the involvement of endogenous adenosine in the action of amitriptyline in this rat model of painful diabetic neuropathy. These data also suggest that topical application of tricyclic antidepressants may be useful in treating neuropathic pain in diabetics.
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Neuroscience letters · Aug 2002
Attentional modulation of human pain processing in the secondary somatosensory cortex: a magnetoencephalographic study.
The influence of attention on the processing of pain in the secondary somatosensory cortex (SII) was analyzed using magnetoencephalography in response to painful infra-red heat stimuli applied to the left hand in six male healthy subjects, aged 22-28 years. Three experimental paradigms were chosen to deliver attention dependent results under comparable levels of vigilance. ⋯ In contrast, further increase of attention from mid-level to high was not accompanied by an additional enhancement of SII activity. It therefore is concluded that activation patterns of SII follow a saturation function which cannot be enlarged by maximizing the relevance of the painful stimuli.
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Neuroscience letters · Jul 2002
Nitric oxide production in hypothalamus of 2-deoxy-D-glucose-treated and food deprived mice.
Nitric oxide (NO) has been suggested to be involved in the regulation of food intake. In the present study, NO metabolite (nitrite and nitrate, NOx) levels in the hypothalamus were determined in hyperphagic mice. In normal mice, NOx levels were higher in the hypothalamus than those in frontal cortex. ⋯ NOx concentration in the hypothalamus decreased in 48 h-food deprived mice. In the frontal cortex, neither 2-DG nor food deprivation affected NOx levels. These results suggest that NO production in the hypothalamus does not increase in 2-DG-elicited hyperphagia and that food deprivation reduces hypothalamic NO, probably by inhibiting NO synthase.
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Neuroscience letters · Apr 2002
Clinical Trial Controlled Clinical TrialThe addition of glyceryltrinitrate to capsaicin cream reduces the thermal allodynia associated with the application of capsaicin alone in humans.
The aim of this study was to determine whether topical application of capsaicin cream causes thermal allodynia and the extent to which this is attenuated by the addition of glyceryltrinitrate (GTN). This was a double blind placebo controlled study of 40 consenting adult subjects. Each of four cream combinations (GTN, capsaicin, GTN/capsaicin and vehicle) were applied to the subjects with at least a 1 day interval between each application. ⋯ Thermal allodynia is usually apparent when warm water is applied to skin containing capsaicin. The thermal allodynia caused by the topical application of capsaicin was significantly reduced by the addition of GTN. The addition of GTN to capsaicin cream significantly reduces the thermal allodynia associated with the application of capsaicin cream alone.
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Neuroscience letters · Apr 2002
Increased production of nitric oxide stimulated by interferon-gamma from peripheral blood monocytes in patients with complex regional pain syndrome.
This study examines immediate nitric oxide (NO) release from monocytes following interleukin-1beta (IL-1beta), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) challenge in patients with complex regional pain syndrome (CRPS). Study patients exhibited the following: (1), mechanical allodynia; (2), evidence of either vasomotor or sudomotor disturbance; and (3), concordant painful allodynia documented with quantitative sensory testing that was temporarily abolished with sympathetic block. ⋯ Subjects with CRPS exhibited a statistically significant increase in NO release in response to IFN-gamma (P<0.012) compared with controls. The NO responses to IFN-gamma in excess of NS (P<0.025) and as the ratio IFN-gamma/NS (P<0.022) were also significantly increased.