Needle-nerve interaction in acupuncture: A morphological study.

Some acupuncture effects are considered to be caused by interaction with nerve structures in and around the acupoints. The aim of the present study was to investigate the nerve structures that interact with the needle in acupuncture and to present their distribution in acupoint tissues. To do this, the microscopic anatomy and its alterations in the vicinity of the needle tract formed after experimental acupuncture in ST36 acupoint in rats were described by histological and immunohistochemical methods. Free nerve endings were seen in the epidermis, and surrounding hair follicles and sebaceous glands in the dermis. Muscle spindles and larger nerve fibres close to blood vessels were also observed deeper, in the muscular plane. Needling of the acupoint caused destruction and displacement of hair follicles together with their free nerve endings. Deeper, some muscle spindles and smaller nerves were displaced and disrupted. Larger nerves were not destroyed, but rather pushed aside by the needle. Furthermore, needle impact also caused degranulation of mast cells near the needle tract. The findings suggest multiple ways of interaction between acupuncture needle and the nerve structures of the acupoint. Acupuncture combines destruction, disruption and displacement of nerve structures, together with additional interaction with mast cells. Those mechanisms are involved in eliciting the needling sensation and are possibly associated with the systemic effect of acupuncture.

ACE2 expression in human dorsal root ganglion sensory neurons: implications for SARS-CoV-2 virus-induced neurological effects

SARS-CoV-2 has created a global crisis. COVID-19, the disease caused by the virus, is characterized by pneumonia, respiratory distress and hypercoagulation and is often fatal1. An early sign of infection is loss of smell, taste and chemesthesis - loss of chemical sensation2. Other neurological effects of the disease have been described, but not explained3,4. We show that human dorsal root ganglion (DRG) neurons express the SARS-CoV-2 receptor5,6, ACE2. ACE2 mRNA is expressed by a subset of nociceptors that express MRGPRD mRNA suggesting that SARS-CoV-2 may gain access to the nervous system through entry into neurons that form free-nerve endings at the outer-most layers of skin and luminal organs. Therefore, sensory neurons are a potential target for SARS-CoV-2 invasion of the nervous system.

Innervation of the thoracolumbar fascia

The aim of the study was to obtain information on the sensory functions of the thoracolumbar fascia (TLF). The types of nerve fibres present in the TLF were visualized with specific antibodies to neuropeptides and sympathetic fibres. Most data were obtained from the TLF in rats, but some findings from the human fascia are also included. The only receptive nerve ending found was the free nerve ending, i.e. no corpuscular receptors existed in our specimen. An exclusive innervation with free nerve endings speaks for a nociceptive function, but the TLF may also fulfill proprioceptive functions, since many of the free nerve endings have a low mechanical threshold. Most of the fibres could be visualized with antibodies to CGRP [calcitonin gene- related peptide (CGRP)] and SP [substance P (SP)]. The latter ones most likely were nociceptors. The TLF contained a great proportion of postganglionic sympathetic fibres, which may be vasoconstrictors. A comparison between an inflamed and intact fascia showed an increase of the CGRP- and SP-positive fibres in the inflamed TLF. This finding could be one explanation for the low back pain of many patients, since practically all lesions of the fascia are accompanied by a sterile inflammation.

Histopathological analysis of the synovium in trapeziometacarpal osteoarthritis

Dorsoradial and anterior oblique ligaments were harvested during surgery in 13 patients with symptomatic trapeziometacarpal osteoarthritis, which had been graded preoperatively by a modified Eaton-Littler radiographic grading. Ligaments, including the periligamentous synovium, were stained with S100 protein, neurotrophic receptor p75, protein gene product 9.5, calcitonin gene related peptide, acetylcholine, substance P, neuropeptide Y, noradrenaline, N-methyl-D-aspartate-receptor and Met/Leu-enkephalin. The synovium was classified as showing no, low-grade or high-grade synovitis. Free nerve endings had higher immunoreactivity for substance P than for N-methyl-D-aspartate-receptor, enkephalin and noradrenaline. The synovial stroma had less immunoreactivity for N-methyl-D-aspartate-receptor than for noradrenaline, substance P and calcitonin gene related peptide. There was no relation between the grade of osteoarthritis and the visual pain analogue scale, synovitis score, immunoreactivity of all antibodies and quantity of free nerve endings or blood vessels. Synovium in trapeziometacarpal joint osteoarthritis produces several neuromediators causing a polymodal neurogenic inflammation and which may serve as biomarkers for osteoarthritis or therapeutic targets.

Neuroanatomical distribution of sensory receptors in the human elbow joint capsule

Background The topographic arrangement of sensory receptors in the human elbow joint capsule is pertinent to their role in the transmission of neural signals. The signals from stimuli in the joint are concisely delivered via afferent pathways to allow recognition of pain and proprioception. Sensory receptors in the elbow joint include mechanoreceptors and free nerve endings acting as nociceptors, although the distribution of each of the structures has not been determined, despite their importance for the integrity of the joint. We therefore aimed to investigate the neuroanatomical distribution and densities of mechanoreceptors and free nerve endings in the capsule of the elbow, at the same time as considering surgical approaches that would result in the minimum insult to them. Methods Four elbow joint capsules were harvested from fresh cadavers. The specimens were carefully separated from adjacent osteoligamentous attachments and the capsular complex was stained with a modified gold chloride method. Evaluations of free nerve endings, and Golgi, Ruffini and Pacinian corpuscles were performed under an inverted light microscope. The number and density of each structure were recorded. Results Ruffini corpuscles observed to be the dominant mechanoreceptor type. No Golgi corpuscle was observed. Free nerve endings were found at the highest density at posterodistal sites, whereas mechanoreceptors were most frequent at bony attachment sites. Conclusions A consistent distribution pattern of articular sensory receptors was observed, which allows further understanding of elbow pathology. An awareness of the neuroanatomical distribution of sensory receptors in the elbow joint capsule may allow their preservation during surgical procedures for elbow joint pathology.