Neuroscience letters
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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.
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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
Methodologic factors which contribute to variations in experimental pain threshold reported for older people.
Using the same study groups and psychophysical methods, we have tested the hypothesis that variations in pain threshold with advancing age are best explained by variations in stimulus duration. Fifteen young adults and 15 older people without clinical evidence of neurologic disease or psychologic dysfunction had pain thresholds determined with heat and electrical stimuli using the method of limits; for electrical stimulation a double random staircase design was used. ⋯ It was found that older people have an increased threshold for thermal and electrically induced pain if the stimulus duration is kept short. This result explains much of the variability in age associated pain threshold in the literature.
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Spatial integration of cold pressor pain (CPP) in the hand was studied in healthy human subjects by measuring the latency to the ice water-induced first pain sensation with and without conditioning CPP. CPP alone showed a marked spatial summation effect. ⋯ A decrease in the test stimulus area increased the suppressive effect by conditioning CPP. Thus, CPP shows spatial summation or inhibition depending on experimental parameters.
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Neuroscience letters · May 2004
Selective C-fiber deafferentation of the spinal dorsal horn prevents lesion-induced transganglionic transport of choleragenoid to the substantia gelatinosa in the rat.
The effect of neonatal capsaicin treatment, producing selective elimination of almost all unmyelinated C-fiber sensory axons, was studied on lesion-induced transganglionic labelling of the substantia gelatinosa of the spinal cord by choleragenoid. In both control and capsaicin-pretreated rats, the injection of choleragenoid-horseradish peroxidase conjugate into the intact sciatic nerves resulted in intense labelling only of the deeper layers of the spinal dorsal horn. In the control but not the capsaicin-pretreated rats, the injection of the tracer into sciatic nerves transected 2 weeks previously produced an intense homogeneous labelling of the substantia gelatinosa. It is concluded that the uptake and axonal transport of choleragenoid by capsaicin-sensitive C-fiber afferents may be accounted for by the lesion-induced transganglionic labelling of the substantia gelatinosa, rather than by A-fiber sprouting.