Changes in TRPV1 Receptor, CGRP, and BDNF Expression in Rat Dorsal Root Ganglion with Resiniferatoxin-Induced Neuropathic Pain: Modulation by Pulsed Radiofrequency Applied to the Sciatic Nerve.

Pulsed radiofrequency (PRF) is a safe method of treating neuropathic pain by generating intermittent electric fields at the needle tip. Resiniferatoxin (RTX) is an ultrapotent agonist of transient receptor potential vanilloid subtype-1 (TRPV1) receptors. We investigated the mechanism of PRF using a rat model of RTX-induced neuropathic pain. After administering RTX intraperitoneally, PRF was applied to the right sciatic nerve. We observed the changes in TRPV1, calcitonin gene-related peptide (CGRP), and brain-derived neurotrophic factor (BDNF) in the dorsal root ganglia by western blotting. Expressions of TRPV1 and CGRP were significantly lower in the contralateral (RTX-treated, PRF-untreated) tissue than in control rats (p<0.0001 and p<0.0001, respectively) and the ipsilateral tissues (p<0.0001 and p<0.0001, respectively). BDNF levels were significantly higher in the contralateral tissues than in the control rats (p<0.0001) and the ipsilateral tissues (p<0.0001). These results suggest that, while TRPV1 and CGRP are decreased by RTX-induced neuronal damage, increased BDNF levels result in pain development. PRF may promote recovery from neuronal damage with concomitant restoration of TRPV1 and CGRP, and exert its analgesic effect by reversing BDNF increase. Further research is required to understand the role of TRPV1 and CGRP restoration in improving mechanical allodynia.

Selective optogenetic activation of NaV1.7-expressing afferents in NaV1.7-ChR2 mice induces nocifensive behavior without affecting responses to mechanical and thermal stimuli.

In small and large spinal dorsal root ganglion neurons, subtypes of voltage-gated sodium channels, such as NaV1.7, NaV1.8, and NaV1.9 are expressed with characteristically localized and may play different roles in pain transmission and intractable pain development. Selective stimulation of each specific subtype in vivo may elucidate its role of each subtype in pain. So far, this has been difficult with current technology. However, Optogenetics, a recently developed technique, has enabled selective activation or inhibition of specific neural circulation in vivo. Moreover, optogenetics had even been used to selectively excite NaV1.8-expressing dorsal root ganglion neurons to induce nocifensive behavior. In recent years, genetic modification technologies such as CRISPR/Cas9 have advanced, and various knock-in mice can be easily generated using such technology. We aimed to investigate the effects of selective optogenetic activation of NaV1.7-expressing afferents on mouse behavior. We used CRISPR/Cas9-mediated homologous recombination to generate bicistronic NaV1.7-iCre knock-in mice, which express iCre recombinase under the endogenous NaV1.7 gene promoter without disrupting NaV1.7. The Cre-driver mice were crossed with channelrhodopsin-2 (ChR2) Cre-reporter Ai32 mice to obtain NaV1.7iCre/+;Ai32/+, NaV1.7iCre/iCre;Ai32/+, NaV1.7iCre/+;Ai32/Ai32, and NaV1.7iCre/iCre;Ai32/Ai32 mice. Compared with wild-type mice behavior, no differences were observed in the behaviors associated with mechanical and thermal stimuli exhibited by mice of the aforementioned genotypes, indicating that the endogenous NaV1.7 gene was not affected by the targeted insertion of iCre. Blue light irradiation to the hind paw induced paw withdrawal by mice of all genotypes in a light power-dependent manner. The threshold and incidence of paw withdrawal and aversive behavior in a blue-lit room were dependent on ChR2 expression level; the strongest response was observed in NaV1.7iCre/iCre;Ai32/Ai32 mice. Thus, we developed a non-invasive pain model in which peripheral nociceptors were optically activated in free-moving transgenic NaV1.7-ChR2 mice.

Extracellular signal-regulated kinase phosphorylation enhancement and NaV1.7 sodium channel upregulation in rat dorsal root ganglia neurons contribute to resiniferatoxin-induced neuropathic pain: The efficacy and mechanism of pulsed radiofrequency therapy.

Pulsed radiofrequency (PRF) therapy is one of the most common treatment options for neuropathic pain, albeit the underlying mechanism has not been hitherto elucidated. In this study, we investigated the efficacy and mechanism of PRF therapy on resiniferatoxin (RTX)-induced mechanical allodynia, which has been used as a model of postherpetic neuralgia (PHN). Adult male rats were intraperitoneally injected with a vehicle or RTX. Furthermore, PRF current was applied on a unilateral sciatic nerve in all RTX-treated rats. On both ipsilateral and contralateral sides, the paw mechanical withdrawal thresholds were examined and L4-6 dorsal root ganglia (DRG) were harvested. In the DRG of rats with RTX-induced mechanical allodynia, NaV1.7, a voltage-gated Na+ channel, was upregulated following the enhancement of extracellular signal-regulated kinase phosphorylation. Early PRF therapy, which was applied 1 week after RTX exposure, suppressed this NaV1.7 upregulation and showed an anti-allodynic effect; however, late PRF therapy, which was applied after 5 weeks of RTX exposure, failed to inhibit allodynia. Interestingly, late PRF therapy became effective after daily tramadol administration for 7 days, starting from 2 weeks after RTX exposure. Both early PRF therapy and late PRF therapy combined with early tramadol treatment suppressed NaV1.7 upregulation in the DRG of rats with RTX-induced mechanical allodynia. Therefore, NaV1.7 upregulation in DRG is related to the development of RTX-induced neuropathic pain; moreover, PRF therapy may be effective in the clinical management of patients with PHN via NaV1.7 upregulation inhibition.

Upregulation of ERK phosphorylation in rat dorsal root ganglion neurons contributes to oxaliplatin-induced chronic neuropathic pain.

Oxaliplatin is the first-line chemotherapy for metastatic colorectal cancer. Unlike other platinum anticancer agents, oxaliplatin does not result in significant renal impairment and ototoxicity. Oxaliplatin, however, has been associated with acute and chronic peripheral neuropathies. Despite the awareness of these side-effects, the underlying mechanisms are yet to be clearly established. Therefore, in this study, we aimed to understand the factors involved in the generation of chronic neuropathy elicited by oxaliplatin treatment. We established a rat model of oxaliplatin-induced neuropathic pain (4 mg kg-1 intraperitoneally). The paw withdrawal thresholds were assessed at different time-points after the treatment, and a significant decrease was observed 3 and 4 weeks after oxaliplatin treatment as compared to the vehicle treatment (4.4 ± 1.0 vs. 16.0 ± 4.1 g; P < 0.05 and 4.4 ± 0.7 vs. 14.8 ± 3.1 g; P < 0.05, respectively). We further evaluated the role of different mitogen-activated protein kinases (MAPKs) pathways in the pathophysiology of neuropathic pain. Although the levels of total extracellular signal-regulated kinase (ERK) 1/2 in the dorsal root ganglia (DRG) were not different between oxaliplatin and vehicle treatment groups, phosphorylated ERK (p-ERK) 1/2 was up-regulated up to 4.5-fold in the oxaliplatin group. Administration of ERK inhibitor PD98059 (6 µg day-1 intrathecally) inhibited oxaliplatin-induced ERK phosphorylation and neuropathic pain. Therefore, upregulation of p-ERK by oxaliplatin in rat DRG and inhibition of mechanical allodynia by an ERK inhibitor in the present study may provide a better understanding of intracellular molecular alterations associated with oxaliplatin-induced neuropathic pain and help in the development of potential therapeutics.

A case of severe acute exacerbation of Yokkaichi asthma treated with a vibrating mesh nebulizer.

Yokkaichi asthma was one of the most common environmental pollution diseases in Japan in the 1960s and 1970s. The problem of air pollution in Yokkaichi was solved in the 1970s. However, mortality and life expectancy were still affected by the late effects of air pollution in patients with Yokkaichi asthma even in the 2000s. In this case report, we described the experience of successful treatment of a patient with severe asthmatic status due to Yokkaichi asthma. A 40s-year-old man, who was officially certified as a patient with Yokkaichi asthma from his infancy, was admitted to hospital due to acute exacerbation of asthma. Mechanical ventilation, intravenous administration of aminophylline and dexamethasone, enteral administration of montelukast, and a transdermal patch of tulobuterol were started. However, because of the lack of improvement in clinical status, inhalation of procaterol using vibrating mesh nebulizer systems was started. Inhalation of procaterol was used three times a day. After using the vibrating mesh nebulizer, respiratory system compliance and hypercapnia rapidly improved. Bilateral expiratory wheezing was diminished. Weaning from mechanical ventilation was initiated, and on the eighth day of mechanical ventilation, the patient was extubated. Although intractable respiratory failure with decreased respiratory system compliance resulting from the late effects of air pollution and a long-time asthmatic inflammatory condition was observed, the use of a vibrating mesh nebulizer for the inhaled administration of procaterol was useful to relieve severe bronchospasm due to Yokkaichi asthma.

[Anchor Fast endotracheal tube securing device for a pediatric patient during therapeutic hypothermia].

A 5-year-old girl was admitted to our hospital after resuscitation from cardiac arrest due to near-drowning accident in a river. On admission, Glasgow Coma Scale score was 7; arterial blood pressure was 113/73 mm Hg; heart rate was 157 beats x min(-1), and percutaneous oxygen saturation was 99% on 10 l x min(-1) of oxygen. The patient was intubated with a 5.0 mm internal diameter endotracheal tube, and therapeutic hypothermia was started for neural protection. Hypothermia in the target temperature of 34 degrees C was maintained for 24 hours using Arctic Sun System. Although the patient had been sedated with fentanyl 0.6-1.2 microg x kg(-1) x hr(-1), midazolam 0.2-0.4 mg x kg(-1) x hr(-1) and dexmedetomidine 0.6-1.0 mirog x kg(-1) x hr(-1), agitation increased during the rewarming period following hypothermia. To avoid accidental extubation, we used Anchor Fast as a device for securing oral endotracheal tube. Anchor Fast kept the tube position properly even though the patient was turned or moved. Seventy-two hours later, she was rewarmed and extubated as scheduled. Ten days after admission, she was discharged without any neurological deficits.

New insights concerning insulin synthesis and its secretion in rat hippocampus and cerebral cortex: amyloid-ß1-42-induced reduction of proinsulin level via glycogen synthase kinase-3ß.

The reduction of insulin levels in hippocampal areas is associated with Alzheimer's disease. The present study using rat brain explores the mechanisms of insulin synthesis and secretion, as well as amyloid-ß1-42 (Aß(1-42))-induced reduction of proinsulin expression. After confirming the expression of insulin mRNA and proinsulin in rat brain, we visualized and analyzed the motion of insulin secretion in rat hippocampal neurons using pH-sensitive green fluorescent protein (pHluorin) fused to the insulin. In the rat hippocampal neurons expressing insulin-pHluorin, time-lapse confocal laser scanning microscopy revealed the appearance of fluorescent spots induced by depolarization after stimulation with 50 mM KCl. In these fluorescent spots, Ca(2+)-dependent activator protein for secretion 2 (CAPS2), which is the regulator of the dense-core vesicle involving neuronal peptides, was co-localized with insulin-pHluorin. However, Aß(1-42)-induced reduction of proinsulin in rat hippocampal neurons was inhibited by treatment with lithium and transfection with glycogen synthase kinase-3ß (GSK-3ß) siRNA. These results demonstrate that synthesized insulin is secreted from rat hippocampal and cortical neuron's dense-core vesicles, and that activation of GSK-3ß in Aß(1-42)-induced Alzheimer's model hippocampal neurons decreases the insulin synthesis.

[Anesthetic considerations for thymectomy in a patient having an anti-acetylcholine receptor antibody without myasthenia gravis].

A patient having an anti-acetylcholine receptor (AChR) antibody without myasthenia gravis was scheduled for thymectomy. Neuromuscular blockade monitoring showed a normal response to vecuronium in the patient. This finding suggests that sensitivities to neuromuscular blocking agents in the patients depend not on the titers of the antibody but also on the presence or absence of the preoperative symptoms such as muscle weakness. It is, however, recommended that neuromuscular blocking agents should be administered carefully under monitoring the neuromuscular function, as is the case for myasthenia gravis, because little is understood about the effect of neuromuscular blocking agent on the neuromuscular function in the asymptomatic patients having anti-AChR antibody.