European journal of pain : EJP
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Recent studies revealed an increased prescription rate of opioids for elderly patients suffering bone fractures. To gain further insight, we conducted face-to-face interviews in the present study to compare the opioid intake between patients with low-energy fractures and patients suffering from internal diseases. ⋯ This study is based on face-to-face interviews with patients, including details about side effects and fracture history, providing a more pronounced picture of the relation of opioid intake and risk of fracture.
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Parathyroid hormone-related peptide (PTHrP) is associated with advanced tumor growth and metastasis, especially in breast, prostate and myeloma cancers that metastasize to bones, resulting in debilitating chronic pain conditions. Our recent studies revealed that the receptor for PTHrP, PTH1R, is expressed in mouse DRG sensory neurons, and its activation leads to flow-activation and modulation of TRPV1 channel function, resulting in peripheral heat and mechanical hypersensitivity. In order to verify the translatability of our findings in rodents to humans, we explored whether this signalling axis operates in primary human DRG sensory neurons. ⋯ Furthermore, exposure of cultured human DRG neurons to PTHrP leads to slow-sustained activation of TRPV1 and modulation of capsaicin-induced channel activation. Both activation and modulation of TRPV1 by PTHrP were dependent on PKC activity. Our findings suggest that functional PTHrP/PTH1R-TRPV1 signalling exists in human DRG neurons, which could contribute to local nociceptor excitation in the vicinity of metastatic bone tumor microenvironment.
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Preclinical research for neuropathic pain has depended primarily on the use of behavioural nociceptive testing that is sensory-discriminatory-based and reflexive in nature. This can be particularly problematic in spinal cord injury (SCI)-associated neuropathic pain research where hyperreflexia may develop thus confounding interpretation of reflexive responses as pain symptoms. To address this, we have designed an affective-motivational-based Overground System that has interchangeable floors to allow examination of nociceptive behaviours in response to mechanical and cold stimuli prior to and following spinal cord injury. ⋯ We have designed an Overground System that is easy to establish and addresses a major concern in preclinical pain research by providing a cognitive- and motivational-based system for hypersensitivity detection. The affective-motivational-based Overground System allows examination of pain-like behaviours in response to cold (thermal) and rough (mechanical) stimulation prior to and following spinal cord injury. This system provides a more holistic and comprehensive assessment of nociceptive responses following SCI and helps overcome concerns of hyperreflexia confounding-evoked behavioural outcome measures in SCI models. Further, the incorporation of cognitive and motivational components brings preclinical research closer to replicating the clinical experience of a patient's motivation to participate in rewarding lifestyle activities in relation to their pain.
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Early hyperexcitability activity of injured nerve/neuron is critical for developing sympathetic nerve sprouting within dorsal root ganglia (DRG) since lacosamide (LCM), an anticonvulsant, inhibits Na+ channel. The present study tried to test the potential effect of LCM on inhibiting sympathetic sprouting in vivo. ⋯ Early LCM administration inhibited sympathetic sprouting within DRG in CCD rats via reducing hyperexcitability of neurons. Early LCM administration suppressed neuropathic pain in CCD rats.
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Neuropathic pain is associated with abnormal sensitivity of the central nervous system. Although the mechanism underlying the development of sensitization remains to be fully elucidated, recent studies have reported that neuroplastic changes in the pain circuitry may be involved in hypersensitivity associated with neuropathic pain. However, it is difficult to investigate such phenomena in existing animal pain model. Therefore, in this study, we developed a novel animal model - the circuit plasticity reconstruction (CPR) model - to mimic central sensitization associated with neuroplastic changes. ⋯ This article represents that the CPR model can mimic the neuropathic pain derived by neuroplastic changes. Our findings indicate that the CPR model may aid the development of novel therapeutic strategies for neuropathic pain and in elucidating the mechanisms underlying pain induced by central sensitization and neuroplastic changes.