Role of trigeminal ganglion satellite glial cells in masseter muscle pain hypersensitivity.

Objectives: The underlying mechanism of masseter muscle pain hypersensitivity by sustained masseter muscle contraction (SMMC) is not well understood. This study aimed to examine whether the activation of satellite glial cells in the trigeminal ganglion (TG) contributes to masseter muscle pain hypersensitivity induced by SMMC.

Methods: Electrodes were placed on the masseter muscle fascia of rats to induce strong contractions, by daily electrical stimulation.

Fibroblast-derived IL-33 exacerbates orofacial neuropathic pain via the activation of TRPA1 in trigeminal ganglion neurons.

Damage to the peripheral nerves of trigeminal ganglion (TG) neurons leads to intractable orofacial neuropathic pain through the induction of neuroinflammation. However, the details of this process are not yet fully understood. Here, we found that fibroblast-derived interleukin (IL)-33 was required for the development of mechanical allodynia in whisker pad skin following infraorbital nerve injury (IONI).

Ageing-Related Macrophage Polarisation in the Trigeminal Ganglion Enhances Incisional Intraoral Pain.

Objective: Although macrophage polarisation in the trigeminal ganglion (TG) is crucial in orofacial pain hypersensitivity, the effect of ageing-related changes and their involvement in intra-oral nociception remains unclear. We assessed the effect of ageing-related macrophage polarisation in TG on intra-oral mechanical pain hypersensitivity following palatal mucosal incision using senescence-accelerated mice (SAM)-prone8 (SAMP8) and SAM-resistant 1 (SAMR1).

Materials And Methods: Mechanical head-withdrawal reflex threshold (MHWRT) of the palatal mucosa was measured for 21 days after palatal mucosal incision.

Potassium nitrate suppresses hyperactivities of Vc neurons of the model with dentin hypersensitivity.

Objective: Potassium nitrate (KNO) suppresses nociception induced by dental hypersensitivity (HYS). We aimed to examine the effects of KNO on the neural activity of the trigeminal spinal subnucleus caudalis (Vc) in HYS model rats.

Methods: KNO or vehicle was applied to the exposed dentin of HYS rats for 3 days.

Non-neuronal cells act as crucial players in neuropathic orofacial pain.

Background: Following peripheral nerve damage, various non-neuronal cells are activated, triggering accumulation in the peripheral and central nervous systems, and communicate with neurons. Evidence suggest that neuronal and non-neuronal cell communication is a critical mechanism of neuropathic pain; however, its detailed mechanisms in contributing to neuropathic orofacial pain development remain unclear.

Highlight: Neuronal and non-neuronal cell communication in the trigeminal ganglion (TG) is believed to cause neuronal hyperactivation following trigeminal nerve damage, resulting in neuropathic orofacial pain.

Involvement of oxidative stress in orofacial mechanical pain hypersensitivity following neonatal maternal separation in rats.

Patients with persistent pain have sometimes history of physical abuse or neglect during infancy. However, the pathogenic mechanisms underlying orofacial pain hypersensitivity associated with early-life stress remain unclear. The present study focused on oxidative stress and investigated its role in pain hypersensitivity in adulthood following early-life stress.

Analgesic effect of linalool odor on oral ulcerative mucositis-induced pain in rats.

Oral ulcerative mucositis (OUM) induces severe pain, leading to a low quality of life. Linalool odor exposure has recently been reported to suppress inflammatory pain in the hind paws. However, the analgesic effect of linalool odor on orofacial pain remains unclear.

Involvement of interferon gamma signaling in spinal trigeminal caudal subnucleus astrocyte in orofacial neuropathic pain in rats with infraorbital nerve injury.

: Trigeminal nerve injury causes orofacial pain that can interfere with activities of daily life. However, the underlying mechanism remains unknown, and the appropriate treatment has not been established yet. This study aimed to examine the involvement of interferon gamma (IFN-γ) signaling in the spinal trigeminal caudal subnucleus (Vc) in orofacial neuropathic pain.

M2 macrophage-derived cathepsin S promotes peripheral nerve regeneration via fibroblast-Schwann cell-signaling relay.

Background: Although peripheral nerves have an intrinsic self-repair capacity following damage, functional recovery is limited in patients. It is a well-established fact that macrophages accumulate at the site of injury. Numerous studies indicate that the phenotypic shift from M1 macrophage to M2 macrophage plays a crucial role in the process of axon regeneration.

PAR2-dependent phosphorylation of TRPV4 at the trigeminal nerve terminals contributes to tongue cancer pain.

Objective: This study aimed to clarify the interactions between the tongue and primary afferent fibers in tongue cancer pain.

Methods: A pharmacological analysis was conducted to evaluate mechanical hypersensitivity of the tongues of rats with squamous cell carcinoma (SCC). Changes in trigeminal ganglion (TG) neurons projecting to the tongue were analyzed using immunohistochemistry and western blotting.

Conformational Relaxation Dynamics of Poly(3-hexylthiophene) Photoexcited in Solution as Studied by Femtosecond Time-Resolved Stimulated Raman Spectroscopy in 1190-1550 nm Region.

When a conjugated polymer is photoexcited in solution, its effective conjugation length in the singlet exciton state often increases through the conformational relaxation of the polymer main chain and/or hopping of the excitation. We measured femtosecond time-resolved near-IR stimulated Raman spectra of poly(3-hexylthiophene) (P3HT) photoexcited in four organic solvents for understanding the dynamics of the exciton elongation through the conformational relaxation separately from that through the exciton hopping. In the ring CC stretch frequency region, a band appears at around 1415 cm and decays, while a new band rises at around 1370 cm.

Energy Transfer Characteristics of Lipid Bilayer Membranes of Liposomes Examined with Picosecond Time-Resolved Raman Spectroscopy.

A number of biochemical reactions proceed inside biomembranes. Since the rate of a chemical reaction is influenced by chemical properties of the surrounding environment, it is important to examine the chemical environment inside the biomembranes. Although the energy transfer characteristics are a basic and important property of a reaction medium, experimental investigation of the thermal conducting capabilities of the biomembranes is a challenging task.

Unusual Effect of Minor Change in Ligand Substitution in Modulation of NIR Emission: A Case Study with [L-Zn-Ln] Complexes.

There have been numerous instances of lanthanide NIR emitting material where one or more types of ligands or metal ion-ligand complexes operate as antennas. The antenna's role in NIR emission has also been thoroughly investigated and validated. The emission properties of the different antennae are predicted to differ.

Microglia cause structural remodeling of noradrenergic axon in the trigeminal spinal subnucleus caudalis after infraorbital nerve injury in rats.

The dysfunction of descending noradrenergic (NAergic) modulation in second-order neurons has long been observed in neuropathic pain. In clinical practice, antidepressants that increase noradrenaline levels in the synaptic cleft are used as first-line agents, although adequate analgesia has not been occasionally achieved. One of the hallmarks of neuropathic pain in the orofacial regions is microglial abnormalities in the trigeminal spinal subnucleus caudalis (Vc).

Neonatal Injury Modulates Incisional Pain Sensitivity in Adulthood: An Animal Study.

Neonatal pain experiences including traumatic injury influence negatively on development of nociceptive circuits, resulting in persistent pain hypersensitivity in adults. However, the detailed mechanism is not yet well understood. In the present study, to clarify the pathogenesis of orofacial pain hypersensitivity associated with neonatal injury, the involvement of the voltage-gated sodium channel (Na) 1.

Photoionization of 3-Methylindole Embedded in Sodium Dodecyl Sulfate and Dodecyltrimethylammonium Chloride Micelles: Migration of Electrons Generated in Micelle Cores and Their Solvation in Outside Water.

Electrons were generated in the core of micelles formed by negatively charged sodium dodecyl sulfate (SDS) or positively charged dodecyltrimethylammonium chloride (DTAC) by photoionization of 3-methylindole embedded in the core. The electrons were hydrated after they moved out of the core to the outer aqueous phase. These processes were monitored with femtosecond time-resolved absorption spectroscopy.

Insular cortical descending projections facilitate neuronal responses to noxious but not innoxious stimulation in rat trigeminal spinal subnucleus caudalis.

The insular cortex (IC) receives orofacial nociceptive information. Pyramidal neurons in IC layer V send their axons to various brain regions, such as the trigeminal spinal subnucleus caudalis (Sp5C), parabrachial nucleus, and periaqueductal gray. However, little information has been available about the functions of these descending projections from the IC.

Tear secretion by Diquafosol suppresses the excitability of trigeminal brainstem nuclear complex neurons by reducing excessive P2Y expression in the trigeminal ganglion in dry eye rats.

The P2Y receptor agonist, diquafosol sodium, is commonly used to treat the signs and symptoms of dry eye disease (DE) patients. Although diquafosol improves tear film stability, the neural mechanisms underlying the reduction in ocular pain are not well defined. This study determined if repeated application of diquafosol reduces the sensitization of nociceptive neurons in the lower trigeminal brainstem nuclear complex (TBNC) via peripheral P2Y mechanisms in a rat model for DE.

Age-related Changes in Trigeminal Ganglion Macrophages Enhance Orofacial Ectopic Pain After Inferior Alveolar Nerve Injury.

Background/aim: The ectopic pain associated with inferior alveolar nerve (IAN) injury has been reported to involve macrophage expression in the trigeminal ganglion (TG). However, the effect of age-related changes on this abnormal pain conditions are still unknown. This study sought to clarify the involvement of age-related changes in macrophage expression and phenotypic conversion in the TG and how these changes enhance ectopic mechanical allodynia after IAN transection (IANX).

Decreased PPARgamma in the trigeminal spinal subnucleus caudalis due to neonatal injury contributes to incision-induced mechanical allodynia in female rats.

Whisker pad skin incision in infancy causes the prolongation of mechanical allodynia after re-incision in adulthood. A recent study also proposed the importance of sex differences in pain signaling in the spinal cord. However, the sex difference in re-incision-induced mechanical allodynia in the orofacial region is not fully understood.

Diquafosol sodium reduces neuronal activity in trigeminal subnucleus caudalis in a rat model of chronic dry eye disease.

Patients with persistent and severe dry eye disease (DED) have corneal hypersensitivity, resulting in ocular pain, and diquafosol sodium, a potent P2Y receptor agonist, is commonly used to improve the resultant tear film stability. This study determined the effects of diquafosol instillation on the suppression of trigeminal subnucleus caudalis (Vc) neuronal activity and ocular pain by enhancing tear film stability in the model for chronic DED. The effects of diquafosol on the ocular surface were assessed by the topical application for 28 days, starting from the 14th day since unilateral exorbital gland removal (chronic DED).

Astrocytic and microglial interleukin-1β mediates complement C1q-triggered orofacial mechanical allodynia.

Glial cells, such as microglia and astrocytes, in the trigeminal spinal subnucleus caudalis (Vc) are activated after trigeminal nerve injury and interact with Vc neurons to contribute to orofacial neuropathic pain. Complement C1q released from microglia has been reported to activate astrocytes and causes orofacial mechanical allodynia. However, how C1q-induced phenotypic alterations in Vc astrocytes are involved in orofacial pain remains to be elucidated.

Effect of cisplatin on oral ulcer-induced nociception in rats.

Objective: The aim of this study is to investigate effects of cisplatin preadministration on oral ulcerative mucositis-induced nociception by using an experimental model of rats.

Design: After two rounds of cisplatin administration, oral ulcers developed with topical acetic acid treatment in rats. Spontaneous mouth rubbing behavior was observed as spontaneous nociceptive behavior in a plastic cage.

Sequence-dependent thymine dimerization and lifetimes of the photoexcited state of oligonucleotides.

DNA-sequence-dependent thymine-thymine (TT) dimerization was investigated from the perspective of the UV-induced charge transfer state. Steady-state and transient absorption measurements suggest that the relatively small oxidation potential and long-lived charge transfer state at the neighboring nucleobases of the TT site may reduce DNA lesion accumulation.