Electroacupuncture Reduces the Effects of Acute Noxious Stimulation on the Electrical Activity of Pain-Related Neurons in the Hippocampus of Control and Neuropathic Pain Rats

Brain nuclei and neural circuits in neuropathic pain and brain modulation mechanisms of acupuncture: a review on animal-based experimental research

Neuropathic pain (NP) is known to be associated with abnormal changes in specific brain regions, but the complex neural network behind it is vast and complex and lacks a systematic summary. With the help of various animal models of NP, a literature search on NP brain regions and circuits revealed that the related brain nuclei included the periaqueductal gray (PAG), lateral habenula (LHb), medial prefrontal cortex (mPFC), and anterior cingulate cortex (ACC); the related brain circuits included the PAG-LHb and mPFC-ACC. Moreover, acupuncture and injurious information can affect different brain regions and influence brain functions via multiple aspects to play an analgesic role and improve synaptic plasticity by regulating the morphology and structure of brain synapses and the expression of synapse-related proteins; maintain the balance of excitatory and inhibitory neurons by regulating the secretion of glutamate, γ-aminobutyric acid, 5-hydroxytryptamine, and other neurotransmitters and receptors in the brain tissues; inhibit the overactivation of glial cells and reduce the release of pro-inflammatory mediators such as interleukins to reduce neuroinflammation in brain regions; maintain homeostasis of glucose metabolism and regulate the metabolic connections in the brain; and play a role in analgesia through the mediation of signaling pathways and signal transduction molecules. These factors help to deepen the understanding of NP brain circuits and the brain mechanisms of acupuncture analgesia.

Altered nociception in Alzheimer disease is associated with striatal-enriched protein tyrosine phosphatase signaling

ABSTRACT

Alzheimer disease (AD) is the most common form of dementia, accounting for approximately 60% of cases. In addition to memory loss, changes in pain sensitivity are found in a substantial proportion of patients with AD. However, the mechanism of nociception deficits in AD is still unclear. Here, we hypothesize that the nociception abnormality in AD is due to the aberrant activation of striatal-enriched protein tyrosine phosphatase (STEP) signaling, which modulates proteins related to nociception transduction. Our results indicated that the transgenic mice carrying human amyloid precursor protein (APP) gene had lower sensitivity to mechanical and thermal stimulation than the wild-type group at the ages of 6, 9, and 12 months. These APP mice exhibited elevated STEP activity and decreased phosphorylation of proteins involved in nociception transduction in hippocampi. The pharmacological inhibition of STEP activity using TC-2153 further reversed nociception and cognitive deficits in the APP mice. Moreover, the phosphorylation of nociception-related proteins in the APP mice was also rescued after STEP inhibitor treatment, indicating the key role of STEP in nociception alteration. In summary, this study identifies a mechanism for the reduced nociceptive sensitivity in an AD mouse model that could serve as a therapeutic target to improve the quality of life for patients with AD.

Peripheral Nerve Stimulation in Pain Management: A Systematic Review

BACKGROUND

Peripheral nerve stimulation (PNS) has been increasingly used to manage acute and chronic pain. However, the level of clinical evidence to support its use is not clear.

OBJECTIVES

To assess the clinical evidence of PNS in the treatment of acute or chronic pain.

STUDY DESIGN

A systematic review of the efficacy and safety of PNS in managing acute or chronic pain.

METHODS

Data sources were PubMed, Cochrane Library, Scopus, CINAHL Plus, Google Scholar, and reference lists. The literature search was performed up to December 2019. Study selection included randomized trials, observational studies, and case reports of PNS in acute or chronic pain. Data extraction and methodological quality assessment were performed utilizing Cochrane review methodologic quality assessment and Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment (IPM-QRB) and Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment for Nonrandomized Studies (IPM-QRBNR). The evidence was summarized utilizing principles of best evidence synthesis on a scale of 1 to 5. Data syntheses: 227 studies met inclusion criteria and were included in qualitative synthesis.

RESULTS

Evidence synthesis based on randomized controlled trials (RCTs) and observational studies showed Level I and II evidence of PNS in chronic migraine headache; Level II evidence in cluster headache, postamputation pain, chronic pelvic pain, chronic low back and lower extremity pain; and Level IV evidence in peripheral neuropathic pain, and postsurgical pain. Peripheral field stimulation has Level II evidence in chronic low back pain, and Level IV evidence in cranial pain.

LIMITATIONS

Lack of high-quality RCTs. Meta-analysis was not possible due to wide variations in experimental design, research protocol, and heterogeneity of study population.

CONCLUSIONS

The findings of this systematic review suggest that PNS may be effective in managing chronic headaches, postamputation pain, chronic pelvic pain, and chronic low back and lower extremity pain, with variable levels of evidence in favor of this technique.

Functional characterization of nociceptive mechanisms involved in fibromyalgia and electroacupuncture

The diagnosis and treatment of chronic pain in diseases such as fibromyalgia (FM) are lacking effective standardised protocols that can be widely accessed and implemented by healthcare professionals across the globe. Persistent hyperalgesia and allodynia are characteristic symptoms of FM. This disease has indicated a refractory tendency to conventional treatment ventures, largely resultant from a lack of etiological and pathogenic understanding of the disease development. Emerging evidence indicates that the central nervous system (CNS) plays a critical role in the amplification of pain signals and the neurotransmitters associated therewith. We examined the contribution of the transient receptor potential vanilloid 1 (TRPV1) channel and the major nociceptive components in response to fibromyalgia-like pain in an intermittent cold-stress (ICS) model, in the prefrontal cortex, somatosensory cortex, hippocampus and thalamus areas of the brain. The use of TRPV1 gene deletion mice served to elucidate the role of the TRPV1 receptor in the development and expression of FM-like pain. The results suggest that TRPV1 upregulation is central to the sustained sensation of FM related hyperalgesia. Furthermore, the potential therapeutic benefits of electroacupuncture (EA) at bilateral ST36 acupoint were analysed in order to identify the analgesic effects and mechanism associated with this therapy. The findings indicate that EA treatment successfully attenuated both mechanical and thermal hyperalgesia and suggests that a definitive underlying mechanism of neuromodulation through EA is responsible for providing analgesic benefits to patients suffering from FM.

Electroacupuncture effects on the P2X4R pathway in microglia regulating the excitability of neurons in the substantia gelatinosa region of rats with spinal nerve ligation

Electroacupuncture (EA) has been used to treat neuropathic pain induced by peripheral nerve injury (PNI) by applying an electrical current to acupoints with acupuncture needles. However, the mechanisms by which EA treats pain remain indistinct. High P2X4 receptor (P2X4R) expression levels demonstrate a notable increase in hyperactive microglia in the ipsilateral spinal dorsal horn following PNI. In order to demonstrate the possibility that EA analgesia is mediated in part by P2X4R in hyperactive microglia, the present study performed mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests in male Sprague-Dawley rats that had undergone spinal nerve ligation (SNL). The expression levels of spinal P2X4R were determined using reverse transcription-quantitative PCR, western blotting analysis and immunofluorescence staining. Furthermore, spontaneous excitatory postsynaptic currents (sEPSCs) were recorded using whole-cell patch clamp to demonstrate the effect of EA on synaptic transmission in rat spinal substantia gelatinosa (SG) neurons. The results of the present study demonstrated that EA increased the MWT and TWL and decreased overexpression of P2X4R in hyperactive microglia in SNL rats. Moreover, EA attenuated the frequency of sEPSCs in SG neurons in SNL rats. The results of the present study indicate that EA may mediate P2X4R in hyperactive spinal microglia to inhibit nociceptive transmission of SG neurons, thus relieving pain in SNL rats.

Brain Metabolism in Rats with Neuropathic Pain Induced by Brachial Plexus Avulsion Injury and Treated via Electroacupuncture

PURPOSE

Brain organisation is involved in the mechanism of neuropathic pain. Acupuncture is a common clinical practise in traditional Chinese medicine for the treatment of chronic pain. This study explored electroacupuncture's effects on brain metabolism following brachial plexus avulsion injury (BPAI)-induced pain.

METHODS

A total of 32 female rats were randomised into a normal group, model group, sham electroacupuncture group, and electroacupuncture group. A pain model was included via right BPAI. The electroacupuncture intervention at cervical "Jiaji" points (C5-7) was performed for 11 weeks. The mechanical withdrawal threshold of the non-injured (left) forepaw was measured at the baseline and on days 3, 7, 14, 21, 28, 56, 84, and 112 subsequent to BPAI. Positron emission tomography (PET) was applied to explore metabolic changes on days 28, 84, and 112.

RESULTS

After electroacupuncture, the mechanical withdrawal threshold of the left forepaws was significantly elevated and the effect persisted until 4 weeks after the intervention ceased (p<0.05 or p<0.001). In the sensorimotor-related brain regions, standardised uptake values in the bilateral somatosensory and motor cortices were observed in the electroacupuncture group. Metabolism particularly increased in the right somatosensory cortex. Metabolism changes also occurred in the pain-related brain regions and emotion- and cognition-related brain regions.

CONCLUSION

The present study demonstrated the beneficial effects of electroacupuncture for relieving BPAI-induced neuropathic pain in rats. Electroacupuncture intervention might inhibit maladaptive plasticity in brain areas governing multidimensional functions, especially in sensorimotor- and cognition-related cortices.

Activation and Inactivation of Nicotinic Receptnors in the Dorsal Hippocampal Region Restored Negative Effects of Total (TSD) and REM Sleep Deprivation (RSD) on Memory Acquisition, Locomotor Activity and Pain Perception

Sleep deprivation (SD) is a common issue in today's society. Sleep is essential for proper cognitive functions, including learning and memory. Furthermore, sleep disorders can alter pain information processing. Meanwhile, hippocampal nicotinic receptors have a role in modulating pain and memory. The goal of this study is to investigate the effect of dorsal hippocampal (CA1) nicotinic receptors on behavioral changes induced by Total (TSD) and REM Sleep Deprivation (RSD). A modified water box and multi-platform apparatus were used to induce TSD and RSD, respectively. To investigate the interaction between nicotinic receptors and hippocampus-dependent memory, nicotinic receptor agonist (nicotine) or antagonist (mecamylamine) was injected into the CA1 region. The results showed, nicotine at the doses of 0.001 and 0.1 µg/rat and mecamylamine at the doses of 0.01 and 0.1 µg/rat decreased memory acquisition, while both at the doses of 0.01 and 0.1 µg/rat enhanced locomotor activity. Additionally, all doses used for both drugs did not alter pain perception. Also, 24 h TSD or RSD attenuated memory acquisition with no effect on locomotor activity and only TSD induced an analgesic effect. Intra-CA1 administration of subthreshold dose of nicotine (0.0001 µg/rat) and mecamylamine (0.001 µg/rat) did not alter memory acquisition, pain perception and locomotor activity in sham of TSD/RSD rats. Both drugs reversed all behavioral changes induced by TSD. Furthermore, both drugs reversed the effect of RSD on memory acquisition, while only mecamylamine reversed the effect of RSD on locomotor activity. In conclusion, CA1 nicotinic receptors play a significant role in TSD/RSD-induced behavioral changes.

Sino-Austrian High-Tech Acupuncture Network: Annual Report 2017

The Sino-Austrian High-Tech Acupuncture Research Network was founded in 2005 and has been growing ever since. The network comprises many partners from China and is highly involved in research and education activities. This report introduces the network's activities in the year 2017.

Sino-Austrian High-Tech Acupuncture Network-Annual Report 2016

The Sino-Austrian High-Tech Acupuncture Research Network was founded in 2005 and has been growing ever since. The network comprises many partners from China and is highly involved in research and education activities. This report introduces the network's activities in the year 2016.