Olfactory stimulation Inhibits Nociceptive Signal Processing at the Input Stage of the Central Trigeminal System

A Review of the Effects of Some Extrinsic Factors on Mice Used in Research

Animals have been used in research for over 2,000 y. From very crude experiments conducted by ancient scholars, animal research, as a science, was refined over hundreds of years to what we know it as today. However, the housing conditions of animals used for research did not improve significantly until less than 100 years ago when guidelines for housing research animals were first published. In addition, it was not until relatively recently that some extrinsic factors were recognized as a research variable, even when animals were housed under recommended guidelines. For example, temperature, humidity, light, noise, vibration, diet, water, caging, bedding, etc., can all potentially affect research using mice, contributing the inability of others to reproduce published findings. Consequently, these external factors should be carefully considered in the design, planning, and execution of animal experiments. In addition, as recommended by others, the housing and husbandry conditions of the animals should be described in detail in publications resulting from animal research to improve study reproducibility. Here, we briefly review some common, and less common, external factors that affect research in one of the most popular animal models, the mouse.

Identification of brain areas in mice with peak neural activity across the acute and persistent phases of post-traumatic headache

BACKGROUND

Post-traumatic headache is very common after a mild traumatic brain injury. Post-traumatic headache may persist for months to years after an injury in a substantial proportion of people. The pathophysiology underlying post-traumatic headache remains unknown but is likely distinct from other headache disorders. Identification of brain areas activated in acute and persistent phases of post-traumatic headache can provide insights into the underlying circuits mediating headache pain. We used an animal model of mild traumatic brain injury-induced post-traumatic headache and c-fos immunohistochemistry to identify brain regions with peak activity levels across the acute and persistent phases of post-traumatic headache.

METHODS

Male and female C57BL/6 J mice were briefly anesthetized and subjected to a sham procedure or a weight drop closed-head mild traumatic brain injury . Cutaneous allodynia was assessed in the periorbital and hindpaw regions using von Frey filaments. Immunohistochemical c-fos based neural activity mapping was then performed on sections from whole brain across the development of post-traumatic headache (i.e. peak of the acute phase at 2 days post- mild traumatic brain injury), start of the persistent phase (i.e. >14 days post-mild traumatic brain injury) or after provocation with stress (bright light). Brain areas with consistent and peak levels of c-fos expression across mild traumatic brain injury induced post-traumatic headache were identified and included for further analysis.

RESULTS

Following mild traumatic brain injury, periorbital and hindpaw allodynia was observed in both male and female mice. This allodynia was transient and subsided within the first 14 days post-mild traumatic brain injury and is representative of acute post-traumatic headache. After this acute post-traumatic headache phase, exposure of mild traumatic brain injury mice to a bright light stress reinstated periorbital and hindpaw allodynia for several hours - indicative of the development of persistent post-traumatic headache. Acute post-traumatic headache was coincident with an increase in neuronal c-fos labeling in the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and the nucleus accumbens. Neuronal activation returned to baseline levels by the persistent post-traumatic headache phase in the spinal nucleus of the trigeminal caudalis and primary somatosensory cortex but remained elevated in the nucleus accumbens. In the persistent post-traumatic headache phase, coincident with allodynia observed following bright light stress, we observed bright light stress-induced c-fos neural activation in the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and nucleus accumbens.

CONCLUSION

Examination of mild traumatic brain injury-induced changes in peak c-fos expression revealed brain regions with significantly increased neural activity across the acute and persistent phases of post-traumatic headache. Our findings suggest mild traumatic brain injury-induced post-traumatic headache produces neural activation along pain relevant pathways at time-points matching post-traumatic headache-like pain behaviors. These observations suggest that the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and nucleus accumbens may contribute to both the induction and maintenance of post-traumatic headache.

Intranasal trigeminal function in chronic rhinosinusitis: a review

INTRODUCTION

Chronic rhinosinusitis (CRS) affects 5-12% of the general population with significant effects on quality of life. Chronic inflammation also seems to affect intranasal trigeminal sensitivity.

AREAS COVERED

A systematic literature search was done in Scopus, Web of Science, and PubMed in February 2023. The review addressed intranasal trigeminal function in patients with CRS and summarized current knowledge on trigeminal function as it relates to the symptoms, assessment, and treatment of CRS.

EXPERT OPINION

Olfaction and trigeminal function are synergistic and this interaction may contribute to trigeminal dysfunction in CRS. Aside from anatomic blockage through polypoid mucosal changes, trigeminal dysfunction may affect the perception of nasal obstruction in CRS. Upregulated immune defense mechanisms leading to damage of nerve endings, changes in nerve growth factor release or other mechanisms may be responsible for trigeminal dysfunction in CRS. Since the pathophysiology of trigeminal dysfunction in CRS is poorly understood, current treatment recommendations are directed toward the therapy of CRS as an underlying cause, although the effect of surgery and corticosteroids on trigeminal function remains unclear. A standardized and validated trigeminal test that is accessible and easy to use in clinical settings would be beneficial for future studies.

[Evidence-based guideline for neonatal pain management in China (2023)]

Pain disrupts neonatal vital signs and internal environment homeostasis and affects the recovery process, and recurrent pain stimulation is one of the important risk factors for neurodevelopmental disorders and some chronic diseases. In order to standardize pain management practice in neonatal wards in China and effectively prevent and reduce the adverse effects of pain on the physical and mental development of neonates, National Clinical Research Center for Child Health and Diseases (Children's Hospital of Chongqing Medical University) convened a multidisciplinary panel to formulate the evidence-based guideline for neonatal pain management in China (2023 edition) following the principles and methods for the guideline development issued by the World Health Organization. Based on the best evidence and expert consensus, this guideline gives 26 recommendations for nine clinical issues, i.e., the classification and definition of neonatal pain, common sources of pain, pain assessment principles, pain assessment methods, analgesic principle, non-pharmaceutical analgesic methods, pharmaceutical analgesic methods, parental participation in pain management, and recording methods for pain management, so as to provide medical staff with guidance and a decision-making basis for neonatal pain assessment and analgesia management.

Olfactory training reduces pain sensitivity in children and adolescents with primary headaches

Objective

Headache prevalence among children and adolescents has increased over the last few years. Evidence-based treatment options for pediatric headaches remain limited. Research suggests a positive influence of odors on pain and mood. We investigated the effect of repeated exposure to odors on pain perception, headache-related disability, and olfactory function in children and adolescents with primary headaches.

Methods

Eighty patients with migraine or tension-type headache (mean 13.1 ± 3.29 years) participated, of whom 40 underwent daily olfactory training with individually selected pleasant odors for 3 months and 40 received state-of-the-art outpatient therapy as a control group. At baseline and after a 3-month follow-up, olfactory function [odor threshold; odor discrimination; odor identification; comprehensive Threshold, Discrimination, Identification (TDI) score], mechanical detection and pain threshold (quantitative sensory testing), electrical pain threshold, patient-reported outcomes on headache-related disability [Pediatric Migraine Disability Assessment (PedMIDAS)], pain disability [Pediatric Pain Disability Index (P-PDI)], and headache frequency were assessed.

Results

Training with odors significantly increased the electrical pain threshold compared to the control group (U = 470.000; z = -3.177; p = 0.001). Additionally, olfactory training significantly increased the olfactory function (TDI score [t(39) = -2.851; p = 0.007], in particular, olfactory threshold, compared to controls (U = 530.500; z = -2.647; p = 0.008). Headache frequency, PedMIDAS, and P-PDI decreased significantly in both groups without a group difference.

Conclusions

Exposure to odors has a positive effect on olfactory function and pain threshold in children and adolescents with primary headaches. Increased electrical pain thresholds might reduce sensitization for pain in patients with frequent headaches. The additional favorable effect on headache disability without relevant side effects underlines the potential of olfactory training as valuable nonpharmacological therapy in pediatric headaches.

Natural Herbal Non-Opioid Topical Pain Relievers-Comparison with Traditional Therapy

Pain is the predominant symptom of many clinical diseases and is frequently associated with neurological and musculoskeletal problems. Chronic pain is frequent in the elderly, causing suffering, disability, social isolation, and increased healthcare expenses. Chronic pain medication is often ineffective and has many side effects. Nonsteroidal over-the-counter and prescription drugs are frequently recommended as first-line therapies for pain control; however, long-term safety issues must not be neglected. Herbs and nutritional supplements may be a safer and more effective alternative to nonsteroidal pharmaceuticals for pain management, especially when used long-term. Recently, topical analgesic therapies have gained attention as an innovative approach due to their sufficient efficacy and comparatively fewer systemic side effects and drug-drug interactions. In this paper, we overview the main natural herbal pain relievers, their efficacy and safety, and their potential use as topical agents for pain control. Although herbal-derived medications are not appropriate for providing quick relief for acute pain problems, they could be used as potent alternative remedies in managing chronic persistent pain with minimal side effects.

Molecular Organization and Patterning of the Medulla Oblongata in Health and Disease

The medulla oblongata, located in the hindbrain between the pons and the spinal cord, is an important relay center for critical sensory, proprioceptive, and motoric information. It is an evolutionarily highly conserved brain region, both structural and functional, and consists of a multitude of nuclei all involved in different aspects of basic but vital functions. Understanding the functional anatomy and developmental program of this structure can help elucidate potential role(s) of the medulla in neurological disorders. Here, we have described the early molecular patterning of the medulla during murine development, from the fundamental units that structure the very early medullary region into 5 rhombomeres (r7–r11) and 13 different longitudinal progenitor domains, to the neuronal clusters derived from these progenitors that ultimately make-up the different medullary nuclei. By doing so, we developed a schematic overview that can be used to predict the cell-fate of a progenitor group, or pinpoint the progenitor domain of origin of medullary nuclei. This schematic overview can further be used to help in the explanation of medulla-related symptoms of neurodevelopmental disorders, e.g., congenital central hypoventilation syndrome, Wold–Hirschhorn syndrome, Rett syndrome, and Pitt–Hopkins syndrome. Based on the genetic defects seen in these syndromes, we can use our model to predict which medullary nuclei might be affected, which can be used to quickly direct the research into these diseases to the likely affected nuclei.