The voltage‐gated sodium channel NaV1.7 plays a critical role in pain pathways. We generated an epitope‐tagged NaV1.7 mouse that showed normal pain behaviours to identify channel‐interacting proteins. Analysis of NaV1.7 complexes affinity‐purified under native conditions by mass spectrometry revealed 267 proteins associated with Nav1.7 in vivo. The sodium channel β3 (Scn3b), rather than the β1 subunit, complexes with Nav1.7, and we demonstrate an interaction between collapsing‐response mediator protein (Crmp2) and Nav1.7, through which the analgesic drug lacosamide regulates Nav1.7 current density. Novel NaV1.7 protein interactors including membrane‐trafficking protein synaptotagmin‐2 (Syt2), L‐type amino acid transporter 1 (Lat1) and transmembrane P24‐trafficking protein 10 (Tmed10) together with Scn3b and Crmp2 were validated by co‐immunoprecipitation (Co‐IP) from sensory neuron extract. Nav1.7, known to regulate opioid receptor efficacy, interacts with the G protein‐regulated inducer of neurite outgrowth (Gprin1), an opioid receptor‐binding protein, demonstrating a physical and functional link between Nav1.7 and opioid signalling. Further information on physiological interactions provided with this normal epitope‐tagged mouse should provide useful insights into the many functions now associated with the NaV1.7 channel.

18The voltage-gated sodium channel NaV1.7 plays a critical role in pain pathways. 19Besides action potential propagation, NaV1.7 regulates neurotransmitter release, 20integrates depolarizing inputs over long periods and regulates transcription. In order 21 to better understand these functions, we generated an epitope-tagged NaV1.7 mouse 22 that showed normal pain behavior. Analysis of NaV1.7 complexes affinity-purified 23 under native conditions by mass spectrometry revealed 267 NaV1.7 associated 24 proteins including known interactors, such as the sodium channel β3 subunit (Scn3b) 25and collapsin response mediator protein (Crmp2), and novel interactors. Selected 26 novel NaV1.7 protein interactors membrane-trafficking protein synapototagmin-2 27 (Syt2), G protein-regulated inducer of neurite outgrowth 1 (Gprin1), L-type amino acid 28 transporter 1 (Lat1) and transmembrane P24 trafficking protein 10 (Tmed10) together 29 with Scn3b and Crmp2 were validated using co-immunoprecipitation and functional 30 assays. The information provided with this physiologically normal epitope-tagged 31 mouse should provide useful insights into the pain mechanisms associated with 32 NaV1.7 channel function. 33 not peer-reviewed)

Nervous systems are designed to become extra sensitive to afferent nociceptive stimuli under certain circumstances such as inflammation and nerve injury. How pain hypersensitivity comes about is key issue in the field since it ultimately results in chronic pain. Central sensitization represents enhanced pain sensitivity due to increased neural signaling within the central nervous system (CNS). Particularly, much evidence indicates that underlying mechanism of central sensitization is associated with the change of spinal neurons. Extracellular signal-regulated kinases have received attention as key molecules in central sensitization. Previously, we revealed the isoform-specific function of extracellular signal-regulated kinase 2 (Erk2) in spinal neurons for central sensitization using mice with Cre-loxP-mediated deletion of Erk2 in the CNS. Still, how extracellular signal-regulated kinase 5 (Erk5) in spinal neurons contributes to central sensitization has not been directly tested, nor is the functional relevance of Erk5 and Erk2 known. Here, we show that Erk5 and Erk2 in the CNS play redundant and/or distinct roles in central sensitization, depending on the plasticity context (cell types, pain types, time, etc.). We used male mice with Erk5 deletion specifically in the CNS and found that Erk5 plays important roles in central sensitization in a formalin-induced inflammatory pain model. Deletion of both Erk2 and Erk5 leads to greater attenuation of central sensitization in this model, compared to deletion of either isoform alone. Conversely, Erk2 but not Erk5 plays important roles in central sensitization in neuropathic pain, a type of chronic pain caused by nerve damage. Our results suggest the elaborate mechanisms of Erk signaling in central sensitization.

The large-conductance Ca 2+-and voltage-activated K + (BK) channel is formed by four pore-forming subunits encoded by a single Slo1 gene and dually regulated by membrane voltage and intracellular Ca 2+ levels. Recently, accumulating evidence using pharmacological methods suggests that the BK channel are associated with nociceptive sensitization. However, mechanisms underlying the effect of the BK channel on the regulation of pain signaling is still largely unknown. Here, we studied the role of the BK channel in the pain signaling in vivo using mice deficient for Slo1. In a partial sciatic nerve ligation (PSNL) model, Slo1 KO mice showed partially restored thermal hyperalgesia compared to their WT littermates. In microglia from WT mice, p38 MAPK phosphorylation was significantly increased after lysophosphatidic acid (LPA) treatment; conversely, it was not significantly upregulated in microglia from Slo1 KO mice, suggesting that the BK channel contributes to the signaling of microglial hyperactivation. Notably, intrathecal (i.t.) injection of microglia derived from WT mice into Slo1 KO mice before PSNL induced the normal development of hyperalgesia in Slo1 KO mice. These results indicate that the BK channel activation in spinal microglia, but not in neuron, contribute to the induction of neuropathic pain in this PSNL model.

BACKGROUND: Intravenous (IV) infusions of volatile anesthetics in lipid emulsion may increase blood lipid concentration, potentially altering the anesthetic agent’s blood solubility and blood-gas partition coefficient (BGPC). We examined the influence of a low-lipid concentration 20% sevoflurane emulsion on BGPC, and the anesthetic potency of this emulsion using dogs. METHODS: We compared BGPC and anesthetic characteristics in 6 dogs between the IV anesthesia of emulsion and the sevoflurane inhalation anesthesia in a randomized crossover substudy. Minimum alveolar concentrations (MACs) were determined by tail-clamp stimulation by using the up-and-down method. Blood sevoflurane concentration and partial pressure were measured by gas chromatography; end-tidal sevoflurane concentration was measured using a gas monitor. The primary outcome was BGPC at the end of IV anesthesia and inhalation anesthesia. Secondary outcomes were time to loss/recovery of palpebral reflex, finish intubation and awakening, MAC, blood concentration/partial pressure at MAC and awakening, correlation between blood partial pressure and gas monitor, and the safety of emulsions. RESULTS: BGPC showed no difference between IV and inhaled anesthesia (0.859 [0.850–0.887] vs 0.813 [0.791–0.901]; P = .313). Induction and emergence from anesthesia were more rapid in IV anesthesia of emulsion than inhalation anesthesia. MAC of emulsion (1.33% [1.11–1.45]) was lower than that of inhalation (2.40% [2.33–2.48]; P = .031), although there was no significant difference in blood concentration. End-tidal sevoflurane concentration could be estimated using gas monitor during IV anesthesia of emulsion. No major complications were observed. CONCLUSIONS: IV anesthesia with emulsion did not increase the BGCP significantly compared to inhalation anesthesia. It was suggested that the anesthetic potency of this emulsion may be equal to or more than that of inhalation.