Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology
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Electrical low-frequency stimulation (LFS) of cutaneous afferents evokes long-term depression (LTD) of nociception. In vitro studies suggest a sole homosynaptic effect on the conditioned pathway. The present study addresses homotopy of LTD in human nociception and pain. ⋯ Homotopy is probably due to a homosynaptic effect at first nociceptive synapse, but descending inhibitory systems may also be involved. These experiments may help to judge the potency of LTD for future therapy in chronic pain.
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Although laser stimuli activate both Adelta- and C-fibres, the corresponding laser evoked potentials (LEPs) remain restricted to the Adelta-fibre input. Previous studies found C-LEPs after limb stimulation only in subjects with block or clinical impairment of Adelta-fibres. In this study, we aimed at verifying whether in the trigeminal territory the impairment of Adelta-fibres unmasks the C-LEP. ⋯ In clinical studies using the standard laser pulses to evoke the Adelta-LEPs, the finding of absent signals does not indicate a concomitant impairment of C-fibres.