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While the prognosis of patients with Ewing sarcoma (EwS) is improving, little is known about the frequency of pain and its risk factors in survivors of EwS. This study aims to analyse the prevalence and risk factors of pain and its predictive value for recurrence.
Learn More >Partner's responses to pain behaviours play a pivotal role in the patient's adjustment. This study aims to further our knowledge regarding patients' and partners' interpretation of partners' responses to pain behaviours, and the possible discrepancies between patients' and partners' perceptions. Further, this study examines patients' preferred responses to pain behaviours and possible discrepancies between received and preferred responses to pain behaviours.
Learn More >Migraine preventive medications are used to reduce headache frequency, severity, and duration. In patients with chronic migraine (CM), reversion to episodic migraine (EM) is an important treatment goal.
Learn More >Cluster headache (CH) is a highly disabling primary headache disorder. To date, characterization of outcomes in the preventive treatment of episodic CH, including precise definitions of clinically meaningful attack frequency reduction and impact on acute treatment management, is lacking.
Learn More >The Sigma-1 receptor (σ1R) has emerged as an interesting pharmacological target because it inhibits analgesia mediated by mu-opioid receptors (MOR), and also facilitates the development of neuropathic pain. Based on these findings, the recent cloning of the Sigma-2 receptor (σ2R) led us to investigate its potential role as a regulator of opioid analgesia and of pain hypersensitivity in σ2R knockout mice. In contrast to σ1R deficient mice, σ2R knockout mice developed mechanical allodynia following establishment of chronic constriction injury-induced neuropathic pain, which was alleviated by the σ1R antagonist S1RA. The analgesic effects of morphine, [D-Ala, N-MePhe, Gly-ol]-encephalin (DAMGO) and β-endorphin increased in σ1R mice and diminished in σ2R mice. The analgesic effect of morphine was increased in σ2R mice by treatment with S1RA. However, σ2R mice and wild-type mice exhibited comparable antinociceptive responses to the delta receptor agonist [D-Pen2,5]-encephalin (DPDPE), the cannabinoid type 1 receptor agonist WIN55,212-2 and the α2-adrenergic receptor agonist clonidine. Therefore, while σR1 inhibits and σ2R facilitates MOR-mediated analgesia these receptors exchange their roles when regulating neuropathic pain perception. Our study may help identify new pharmacological targets for diminishing pain perception and improving opioid detoxification therapies.
Learn More >The peripheral mu-opioid receptor (MOR) has been recognized as a potential target to provide safer analgesia with reduced central side effects. Although analgesic incompetence of the peripheral MOR in the absence of inflammation was initially identified more than a decade ago, there has been very limited investigation into the underlying signaling mechanisms. Here we identify that G protein-coupled receptor kinase 2 (GRK2) constitutively interacts with the MOR in peripheral sensory neurons to suppress peripheral MOR activity. Brief exposure to bradykinin (BK) causes uncoupling of GRK2 from the MOR and subsequent restoration of MOR functionality in dorsal root ganglion (DRG) neurons. Interestingly, prolonged BK treatment induces constitutive activation of the MOR through a mechanism that involves protein kinase C (PKC) activation. After silencing Raf kinase inhibitory protein (RKIP) by RNA interference, BK-induced constitutive MOR activation is completely abrogated, which agrees with previous findings that BK activates PKC signaling to initiate GRK2 sequestration by RKIP. Furthermore, we demonstrate that constitutive, peripheral MOR activity requires GRK2 uncoupling and that the FDA-approved SSRI paroxetine promotes this state of uncoupling. Collectively, these results indicate that GRK2 tightly regulates MOR functional states and controls constitutive MOR activity in peripheral sensory neurons, supporting the potential for targeting the kinase to provide safer analgesia.
Learn More >Delivering adeno-associated virus (AAV) vectors into the central nervous system of nonhuman primates (NHPs) via the blood or cerebral spinal fluid is associated with dorsal root ganglion (DRG) toxicity. Conventional immune-suppression regimens do not prevent this toxicity, possibly because it may be caused by high transduction rates, which can, in turn, cause cellular stress due to an overabundance of the transgene product in target cells. To test this hypothesis and develop an approach to eliminate DRG toxicity, we exploited endogenous expression of microRNA (miR) 183 complex, which is largely restricted to DRG neurons, to specifically down-regulate transgene expression in these cells. We introduced sequence targets for miR183 into the vector genome within the 3' untranslated region of the corresponding transgene messenger RNA and injected vectors into the cisterna magna of NHPs. Administration of unmodified AAV vectors resulted in robust transduction of target tissues and toxicity in DRG neurons. Consistent with the proposal that immune system activity does not mediate this neuronal toxicity, we found that steroid administration was ineffective in alleviating this pathology. However, including miR183 targets in the vectors reduced transgene expression in, and toxicity of, DRG neurons without affecting transduction elsewhere in the primate's brain. This approach might be useful in reducing DRG toxicity and the associated morbidity and should facilitate the development of AAV-based gene therapies for many central nervous system diseases.
Learn More >The neurokinin-1 receptor (NK1R; encoded by ) is expressed in spinal dorsal horn neurons and has been suggested to mediate itch in rodents. However, previous studies relied heavily on neurotoxic ablation of NK1R spinal neurons, which limited further dissection of their function in spinal itch circuitry. To address this limitation, we leveraged a newly developed mouse line to characterize the role of NK1R spinal neurons in itch. We show that pharmacological activation of spinal NK1R and chemogenetic activation of spinal neurons increases itch behavior in male and female mice, whereas pharmacological inhibition of spinal NK1R suppresses itch behavior. We use fluorescence hybridization (FISH) to characterize the endogenous expression of throughout the superficial and deeper dorsal horn (DDH), as well as the lateral spinal nucleus (LSN), of mouse and human spinal cord. Retrograde labeling studies in mice from the parabrachial nucleus (PBN) show that less than 20% of superficial dorsal horn neurons are spinal projection neurons, and thus the majority of are local interneurons. We then use a combination of hybridization and two-photon Ca imaging of the mouse spinal cord to establish that NK1R and the gastrin-releasing peptide receptor (GRPR) are coexpressed within a subpopulation of excitatory superficial dorsal horn (SDH) neurons. These findings are the first to suggest a role for NK1R interneurons in itch and extend our understanding of the complexities of spinal itch circuitry. The spinal cord is a critical hub for processing somatosensory input, yet which spinal neurons process itch input and how itch signals are encoded within the spinal cord is not fully understood. We demonstrate neurokinin-1 receptor (NK1R) spinal neurons mediate itch behavior in mice and that the majority of NK1R spinal neurons are local interneurons. These NK1R neurons comprise a subset of gastrin-releasing peptide receptor (GRPR) interneurons and are thus positioned at the center of spinal itch transmission. We show NK1R mRNA expression in human spinal cord, underscoring the translational relevance of our findings in mice. This work is the first to suggest a role for NK1R interneurons in itch and extends our understanding of the complexities of spinal itch circuitry.
Learn More >Among the five KCNQ channels, also known as the K7 voltage-gated potassium (K) channels, KCNQ2-KCNQ5 control neuronal excitability. Dysfunctions of KCNQ2-KCNQ5 are associated with neurological disorders such as epilepsy, deafness, and neuropathic pain. Here, we report the cryoelectron microscopy (cryo-EM) structures of human KCNQ4 and its complexes with the opener retigabine or the blocker linopirdine at overall resolutions of 2.5, 3.1, and 3.3 Å, respectively. In all structures, a phosphatidylinositol 4,5-bisphosphate (PIP) molecule inserts its head group into a cavity within each voltage-sensing domain (VSD), revealing an unobserved binding mode for PIP. Retigabine nestles in each fenestration, inducing local shifts. Instead of staying within the central pore, linopirdine resides in a cytosolic cavity underneath the inner gate. Electrophysiological analyses of various mutants corroborated the structural observations. Our studies reveal the molecular basis for the modulatory mechanism of neuronal KCNQ channels and provide a framework for structure-facilitated drug discovery targeting these important channels.
Learn More >Many primary care clinics are resistant to accept new patients taking prescription opioids for chronic pain. It is unclear how much of this practice is specific to individuals who may be perceived to have aberrant opioid use. This study sought to determine whether clinics are more or less willing to accept and prescribe opioids to patients depending on whether their history is more or less suggestive of aberrant opioids use by conducting an audit survey of primary care clinics in 9 states from May to July 2019. Simulated patients taking opioids for chronic pain called each clinic twice, giving one of two scenarios for needing a new provider: their previous physician had either 1) retired or 2) stopped prescribing opioids for unspecified reasons. Clinic willingness to continue prescribing opioids and accept the patient for general primary care were assessed. Of 452 clinics responding to both scenarios (904 calls), 193 (43%) said their providers would not prescribe opioids in either scenario, 146 (32%) said their providers might prescribe in both, and 113 (25%) responded differently to each scenario. Clinics responding differently had greater odds (OR=1.83 CI[1.23,2.76]) of willingness to prescribe when the previous doctor retired than when the doctor had stopped prescribing. These findings suggest that primary care access is limited for patients taking opioids for chronic pain, and differentially further reduced for patients whose histories are suggestive of aberrant use. This denial of care could lead to unintended harms such as worsened pain or conversion to illicit substances.
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