European journal of pain : EJP
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The withdrawal response elicited by a nociceptive stimulus, i.e., evoked pain measure, is commonly used as an efficacy endpoint in neuropathic pain animal models. It, however, has several limitations, which highlight the importance of examining spontaneous pain. The present study describes an automated method for measuring spontaneous pain behaviour in a rat model of neuropathic pain caused by chronic constriction injury (CCI) of sciatic nerve. ⋯ A non-subjective automated method for measuring spontaneous pain behaviour in an animal model of neuropathic pain was established. It is expected that the current system will greatly enhance the analysis of spontaneous pain-related behaviour, which is a predominant symptom in patients with neuropathic pain. The current system may also be valuable in the screening of potential analgesic treatments.
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'Conventional' protocols of high-frequency repetitive transcranial magnetic stimulation (rTMS) delivered to M1 can produce analgesia. Theta burst stimulation (TBS), a novel rTMS paradigm, is thought to produce greater changes in M1 excitability than 'conventional' protocols. After a preliminary experiment showing no analgesic effect of continuous or intermittent TBS trains (cTBS or iTBS) delivered to M1 as single procedures, we used TBS to prime a subsequent session of 'conventional' 10 Hz-rTMS. ⋯ The present results show that the analgesic effects of 'conventional' 10 Hz-rTMS delivered to M1 can be enhanced by TBS priming, at least using iTBS. Interestingly, the application of cTBS and iTBS did not produce opposite modulations, unlike previously reported in other systems. It remains to be determined whether the interest of TBS priming is to generate a simple additive effect or a more specific process of cortical plasticity.
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Neuropathy can lead not only to impaired function but also to sensory sensitization. We aimed to link reduced skin nerve fibre density in different levels to layer-specific functional impairment in neuropathic pain patients and tried to identify pain-specific functional and structural markers. ⋯ Thermal thresholds, axon reflex measurements and assessment of skin innervation density are valuable tools to characterize and quantify peripheral neuropathy and link neuronal function to different layers of the skin. The severity of small fibre neuropathy, however, did not correspond to clinical pain intensity and a specific parameter or pattern that would predict pain intensity in peripheral neuropathy could not be identified.