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.

Formin homology 2 domain-containing 3 (Fhod3) controls neural plate morphogenesis in mouse cranial neurulation by regulating multidirectional apical constriction.

Neural tube closure requires apical constriction during which contraction of the apical F-actin network forces the cell into a wedged shape, facilitating the folding of the neural plate into a tube. However, how F-actin assembly at the apical surface is regulated in mammalian neurulation remains largely unknown. We report here that formin homology 2 domain-containing 3 (Fhod3), a formin protein that mediates F-actin assembly, is essential for cranial neural tube closure in mouse embryos. We found that Fhod3 is expressed in the lateral neural plate but not in the floor region of the closing neural plate at the hindbrain. Consistently, in Fhod3-null embryos, neural plate bending at the midline occurred normally, but lateral plates seemed floppy and failed to flex dorsomedially. Because the apical accumulation of F-actin and constriction were impaired specifically at the lateral plates in Fhod3-null embryos, we concluded that Fhod3-mediated actin assembly contributes to lateral plate-specific apical constriction to advance closure. Intriguingly, Fhod3 expression at the hindbrain was restricted to neuromeric segments called rhombomeres. The rhombomere-specific accumulation of apical F-actin induced by the rhombomere-restricted expression of Fhod3 was responsible for the outward bulging of rhombomeres involving apical constriction along the anteroposterior axis, as rhombomeric bulging was less prominent in Fhod3-null embryos than in the wild type. Fhod3 thus plays a crucial role in the morphological changes associated with neural tube closure at the hindbrain by mediating apical constriction not only in the mediolateral but also in the anteroposterior direction, thereby contributing to tube closure and rhombomere segmentation, respectively.

Up-regulation of NaV1.7 sodium channels expression by tumor necrosis factor-α in cultured bovine adrenal chromaffin cells and rat dorsal root ganglion neurons.

BACKGROUND: Tumor necrosis factor-α (TNF-α) is not only a key regulator of inflammatory response but also an important pain modulator. TNF-α enhances both tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant Na channel currents in dorsal root ganglion (DRG) neurons. However, it remains unknown whether TNF-α affects the function and expression of the TTX-S NaV1.7 Na channel, which plays crucial roles in pain generation. METHODS: We used cultured bovine adrenal chromaffin cells expressing the NaV1.7 Na channel isoform and compared them with cultured rat DRG neurons. The expression of TNF receptor 1 and 2 (TNFR1 and TNFR2) in adrenal chromaffin cells was studied by Semiquantitative reverse transcription-polymerase chain reaction. The effects of TNF-α on the expression of NaV1.7 were examined with reverse transcription-polymerase chain reaction and Western blot analysis. Results were expressed as mean ± SEM. RESULTS: TNFR1 and TNFR2 were expressed in adrenal chromaffin cells, as well as reported in DRG neurons. TNF-α up-regulated NaV1.7 mRNA by 132% ± 9% (N = 5, P = 0.004) in adrenal chromaffin cells, as well as 117% ± 2% (N = 5, P < 0.0001) in DRG neurons. Western blot analysis showed that TNF-α increased NaV1.7 protein up to 166% ± 24% (N = 5, corrected P < 0.0001) in adrenal chromaffin cells, concentration- and time-dependently. CONCLUSIONS: TNF-α up-regulated NaV1.7 mRNA in both adrenal chromaffin cells and DRG neurons. In addition, TNF-α up-regulated the protein expression of the TTX-S NaV1.7 channel in adrenal chromaffin cells. Our findings may contribute to understanding the peripheral nociceptive mechanism of TNF-α.

Differences in clinicopathological characteristics between lipohypertrophy and localized insulin-derived amyloidosis: A scoping review.

Insulin is used as a therapeutic agent in patients with diabetes, and cutaneous lipohypertrophy (LH) and localized insulin-derived amyloidosis (LIDA) are well-known adverse effects associated with insulin injections. The clinical implications, management, assessment methods, and pathological differentiation of LH and LIDA have been recently updated. This review was to update our knowledge of the pathological differentiation, effects of insulin absorption, hypoglycemic events, and recent assessment methods for LH and LIDA. A scoping review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta Analyses extension for Scoping Reviews guidelines. Original studies and case reports in English were also included. PubMed and Scopus databases were searched for keywords to identify papers published up to January 2022. A total of 113 studies were identified through a database search, and 31 were eligible for inclusion in this scoping review. In the 31 studies included in this review, patients with type 2 diabetes had high frequencies of LH and LIDA. LH outcome parameters were assessed using pathological findings and imaging. LIDA is mainly determined by pathological methods, such as hematoxylin and eosin and Congo red staining. Several in vitro and in vivo LIDA models of LIDA have been developed. These results suggest that pathological analysis is required to identify LH and LIDA. It is important to consider LIDA, as it likely influences insulin adsorption and glycemic control. Although several studies have evaluated the LIDA process, little is known about the mechanisms underlying the development of adverse effects associated with insulin injections.

Effectiveness of management protocol for insulin balls in diabetics: a scoping review.

Aim: In order to achieve good glycemic control, the prevention and management of insulin balls is important for diabetic patients during insulin therapy. However, insulin balls still occur within the clinical setting. This review evaluated the effectiveness of programs designed to manage insulin balls. Methods: A scoping review was conducted based on the Japanese and English literature available from a systematic literature search conducted from January 1964 to March 2022. Three databases were searched: PubMed, CINAHL, and Ichushi-Web. Results: A total of 33 articles met the inclusion criteria, which consisted of 3 for prevention management of insulin balls and 30 for management after the occurrence of insulin balls. Findings for prevention management suggested that the insulin injection technique education (avoidance of repeated injections to the same site) and providing knowledge (about insulin balls) prevented the appearance of insulin balls. As for post-occurrence management, insulin injection technique education (avoidance of injections to the insulin ball, avoidance of repeated injections to the same site, and switching the injection site) improved blood glucose control. Hypoglycemia was observed in all studies that included an assessment of hypoglycemia. None of the studies evaluated long-term effects of either preventive or post-occurrence management. Conclusions: Providing insulin injection technique education is an effective management protocol for insulin balls. Moreover, education about hypoglycemia is important for patients with insulin balls. Further studies to investigate the long-term effects in the management of insulin balls are needed.

Involvement of the orexin system in adrenal sympathetic regulation.

Orexin (hypocretin) is a neuropeptide secreted from hypothalamic neurons that is known to be activated during motivated behaviors and active waking. Presently, our knowledge of orexin is mainly limited to the central nervous system, and the involvement of the orexin system in peripheral tissues has received little attention. In the present study, we analyzed the existence of the orexin system in the adrenal medulla, which is part of the sympathetic nervous system. Orexin and its receptors are expressed in the bovine adrenal medulla. Orexins stimulated intracellular calcium changes and epinephrine release from cultured bovine adrenal medullary cells. Applied orexin decreased expression of prepro-orexin, orexin receptor-1 and orexin receptor-2, suggesting negative feedback regulation in the adrenal gland. Our results indicate involvement of the orexin system in the sympathetic regulation of the adrenal medulla.

[Practical pharmacotherapy education "pharmacology role-play": expansion and ingenuity in Medical, Dental, Pharmaceutical and Nursing education.]

Active learning in pharmacology education "pharmacology role-play," in which students pretend to be health professionals and patients and explain diseases and drug treatments. Because pharmacology role-play is based on cases presented in advance and active learning through communication, named Case & Communication based approach (C&C approach). Pharmacology role-play was started in 2010 at the University of Miyazaki, it has been shared by 28 schools in 4 faculties of medicine, pharmacy, dentistry, and nursing (23 medical schools, 1 pharmaceutical school, 2 dental schools, and 2 nursing universities) over the 13 years until 2022. Although it is a common program, it is implemented with diversity while devoting various ingenuity according to the characteristics of the University. Pharmacology role-play is effective in (1) understanding of medical treatment, (2) understanding patient's feelings, (3) improvement of mental attitude and motivation as health professionals (4) positive influence upon study attitude, regardless of universities that conducted the pharmacology role-play. Various efforts include combining with Personal Drugs, developing interprofessional education through joint role-playing by medical students and nursing students, and developing Oriental medicine education through the cases including Kampo medicine. In addition, there are online lectures in response to the Covid-19, and a joint implementation of two universities, all of which are highly effective. The advantage of the multi-institution common program is that a lot of information can be obtained at once, and it is easy to quickly reflect successful ideas. The flexibility and high resilience that can flexibly change the implementation method (face-to-face/remote) according to the situation are also great strengths.

[Improvement of the learning effectiveness of pharmacology role-play by introducing P-drug reports].

Pharmacology role-play works well for students playing the role of the medical doctor or patient, but students without any roles behave just like observers, resulting in a relatively low learning effectiveness. To improve this issue, a personal drug (P-drug) report was introduced to the role-play program. To examine to what extent the P-drug report affected the learning effectiveness of role-play, we performed questionnaire surveys for players and audiences and subsequent nominal logistic regression analysis. The questionnaire topics were (1) understanding of medical treatment, (2) understanding patient's feelings, (3) improvement of awareness and motivation as a medical doctor, and (4) positive influence upon study attitude. In the topics (1) and (2), the statistical analyses in audiences showed significant relationship between the introduction of the report and observer's recognition of the learning effectiveness, indicating the improvement of learning effectiveness after the introduction of the P-drug report. In players, the percentage of high marks was higher than that in audiences, and no significant differences were found between before and after the introduction of the report. In addition, in the free description, many students realized the importance of selection of therapeutic drugs based on P-drug methods. These results suggest that the introduction of the P-drug report seems useful to make all students participate in the activity of role-play with understanding the selection process of therapeutic drugs, and improves the learning effectiveness of role-play especially in observers. It may be useful to combine P-drug with pharmacology role-play in practical pharmacotherapy education.

Why and by How Much is Insulin Absorption Reduced by Insulin-derived Amyloidosis? A Scoping Review.

Insulin therapy is one of the central treatments for diabetes mellitus. Insulin-derived localized amyloidosis (IDLA) is a known skin-related complication of insulin injection. This is one of the causes of poor glycemic control in diabetic patients on insulin therapy. The aim of this study was to review and update the findings on the extent and mechanism of reduced insulin absorption in IDLA. A literature search was conducted on decreased insulin absorption and its mechanisms, and nine references were selected, with seven of these on decreased insulin absorption and four on mechanisms. Insulin absorption at IDLA sites was reported to be 27-94% lower compared with normal sites. In addition, a comparison between nonpalpable and palpable IDLA sites revealed a significant decrease in insulin absorption at the palpable IDLA site. The mechanism of insulin malabsorption was found to be a reduction in insulin absorption at the palpable IDLA sites. Four mechanisms of decreased insulin absorption were identified: decreased subcutaneous blood flow, adsorption of administered insulin onto insulin amyloid fibers, impaired diffusion of insulin subcutaneously, and physical factors such as shaking of the insulin preparation. These mechanisms should be investigated in vivo in the future.

[Practices and challenges of joint education at two medical schools utilizing online pharmacology role-playing].

The pharmacology role-play, in which students impersonate medical personnel and patients to explain illness and drug treatment, is one of the active learning of pharmacology. However, until now, it has been carried out only within one facility, and has not been carried out between different multi-facility facilities with a larger scale. However, the spread of COVID-19 infection in 2020 was a turning point that drastically changed the way of medical school education centered on traditional face-to-face lectures. Above all, remote real-time lessons using Zoom etc. have the advantage that about 300 students can be conducted at multiple facilities without having to gather them in one place at the same time. With the Korona-ka as a strange currency, the infrastructure has been set up to carry out joint education in pharmacological role-playing between different multi-institutions. We are the first in Japan to conduct a pharmacology role-play jointly by Fujita Medical University and Aichi Medical University, so we would like to introduce the contents.

[Introduction of a joint academic project between the Japan Academy of Nursing Science and the Japanese Pharmacological Society: a scoping review on assessment and preventive care of insulin balls].

Japanese Academy of Nursing Science (JANS) and the Japanese Pharmacological Society (JPS) have been conducting human interaction at each other's scientific meeting symposia in a home-and-away fashion since 2018. JANS and JPS have been working on a joint scientific project, "Scoping Review: Insulin Balls" since 2021. At the 95th Annual Meeting of the JPS held in 2022, we reported from a nursing perspective on the theme of "Assessment and preventive care of insulin balls from a scoping review". Subcutaneous injection into insulin balls has been reported to cause poor blood glucose control. Therefore, it is important to prevent insulin balls. In this study, we had the research questions, "What methods are available for assessment of the insulin injection site?" and "What is the care to prevent induration and how effective is it?" and conducted a scoping review. Regarding methods of injection site assessment, most of the literature identified the injection site by palpation, visual examination, and ultrasonography. About the preventive care, there were some reports of insulin balls occurring because patients have been injecting insulin at the same site, even though healthcare professionals instructed them to avoid the same site. Some of the literature had specific teaching methods such as hand site rotation and calendar injection method, and they were reported effective. In the future, we plan to proceed with the review including care after the development of insulin balls.

[Nursing pharmacology education and active-learning.]

Comprehensive pharmacology education in nursing based on the "Patient-oriented Pharmacology" is effective against the improvement of quality of pharmacotherapy and patient satisfaction. Two active learning programs of practical pharmacotherapy for nursing students have been performed in School of Nursing, University of Miyazaki; (1) pharmacotherapy role-play for interprofessional education (IPE) and (2) practical excise for Kampo medicine. Pharmacotherapy role-play for IPE was performed as joint lecture both medical students and nursing students. This pharmacotherapy role-play is named Case & Communication based approach (C&C approach), since it is studied through communication between physicians, nurses and patients based on cases presented beforehand. In the practical excise for Kampo medicine, nursing students studied Kampo medicines and tried to taste 9 frequently used Kampo medicines. These active-learning programs in nursing pharmacology education may be effective for better understanding of pharmacotherapy and patient's feeling, and improvement of students' motivation as a nurse.

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.

Dexmedetomidine and clonidine inhibit the function of Na(v)1.7 independent of α(2)-adrenoceptor in adrenal chromaffin cells.

PURPOSE: Besides being administered systemically for sedation and analgesia, α(2)-agonists such as dexmedetomidine and clonidine have been administered with intrathecal, epidural, or perineural injections, leading to an antinociceptive effect at the spinal cord or peripheral nerve level. However, the mechanism for this remains unclear. In the present study, we examined whether dexmedetomidine and clonidine could inhibit the function of tetrodotoxin-sensitive Na(+) channels, which play important roles in the generation of pain. METHODS: Cultured bovine adrenal chromaffin cells expressing the tetrodotoxin-sensitive Na(v)1.7 Na(+) channel isoform were incubated in KRP buffer containing 2 µCi (22)NaCl for 5 min without or with dexmedetomidine or clonidine in the absence or presence of veratridine, α-scorpion venom, ß-scorpion venom, Ptychodiscus brevis toxin-3 or ouabain. Cells were then washed and counted radioactively. RESULTS: Dexmedetomidine and clonidine reduced veratridine-induced (22)Na(+) influx via Na(v)1.7 in a concentration-dependent manner (EC(50) = 50 µM and 530 µM), even in the presence of ouabain, an inhibitor of Na(+), K(+)-ATPase. Dexmedetomidine and clonidine shifted the concentration-response curve of veratridine for (22)Na(+) influx downward without altering the EC(50) of veratridine. Atipamezole and yohimbine, α(2)-antagonists, did not prevent the inhibition of veratridine-induced (22)Na(+) influx by dexmedetomidine. Dexmedetomidine and clonidine combined with lidocaine induced more inhibition of veratridine-induced (22)Na(+) influx than each drug did individually. Atipamezole and yohimbine did not prevent the lidocaine-enhancing effect of dexmedetomidine and clonidine. CONCLUSION: Dexmedetomidine and clonidine inhibit the function of Na(v)1.7 independent of α(2)-adrenoceptor. These results may lead to a deeper understanding of the peripheral antinociceptive effects of α (2)-agonists.

Effects of sevoflurane on voltage-gated sodium channel Na(v)1.8, Na(v)1.7, and Na(v)1.4 expressed in Xenopus oocytes.

Sevoflurane is widely used as a volatile anesthetic in clinical practice. However, its mechanism is still unclear. Recently, it has been reported that voltage-gated sodium channels have important roles in anesthetic mechanisms. Much attention has been paid to the effects of sevoflurane on voltage-dependent sodium channels. To elucidate this, we examined the effects of sevoflurane on Na(v) 1.8, Na(v) 1.4, and Na(v) 1.7 expressed in Xenopus oocytes. The effects of sevoflurane on Na(v) 1.8, Na(v) 1.4, and Na(v) 1.7 sodium channels were studied by an electrophysiology method using whole-cell, two-electrode voltage-clamp techniques in Xenopus oocytes. Sevoflurane at 1.0 mM inhibited the voltage-gated sodium channels Na(v)1.8, Na(v)1.4, and Na(v)1.7, but sevoflurane (0.5 mM) had little effect. This inhibitory effect of 1 mM sevoflurane was completely abolished by pretreatment with protein kinase C (PKC) inhibitor, bisindolylmaleimide I. Sevoflurane appears to have inhibitory effects on Na(v)1.8, Na(v)1.4, and Na(v) 1.7 by PKC pathways. However, these sodium channels might not be related to the clinical anesthetic effects of sevoflurane.

[The development of online role-play for pharmacological education].

The role-play for pharmacological education has been developed by Yanagita et al. since 2010 and incorporated into the curriculum of more than 20 medical or pharmaceutical universities in Japan. This case and communication based active learning course provides the practice to acqire fundamental competences for drug therapy, through role playing of medical professionals and patients in simulated clinical settings. The online pharmacological role-play for the first time was performed at Tohoku Medical and Pharmaceutical University Faculty of Medicine during the state of emergency in Japan. We found that the online role-play was as useful as face-to-face role-plays to train appropriate drug prescriptions and communication skills in medical students. In this review, we described the course design, preparation, and operation of online role-play for pharmacological education. We also explained the differences, advantages, and disadvantages between online and face-to-face setting. Finally, we gave examples on-going challenges to the effective use of the online role-play as a core curricular model of pharmacological and pharmacotherapeutic education.

How was cognitive behavioural therapy for mood disorder implemented in Japan? A retrospective observational study using the nationwide claims database from FY2010 to FY2015.

OBJECTIVES: To clarify the dissemination status of cognitive behavioural therapy (CBT) in Japan under the national health insurance scheme. DESIGN: Retrospective observational study. SETTING: National Database of Health Insurance Claims and Specific Health Checkups of Japan. PARTICIPANTS: Patients who received CBT under the national health insurance scheme from fiscal years (FY) 2010 to 2015. PRIMARY AND SECONDARY OUTCOME MEASURES: We estimated the change rate and the standardised claim ratio (SCR) for the number of patients receiving CBT and analysed the association between the CBT status and several regional factors. RESULTS: We found that (a) a total of 60 304 patients received CBT during the study period; (b) the number of patients receiving CBT was highest in the first year (-1.8% from FY2010 to FY2015); (c) the number of patients who received CBT per 100 000 population decreased (or remained at zero) in most prefectures (32 out of 47); (d) there was a maximum 424.7-fold difference between prefectures in the standardised claim ratio for CBT and (e) the number of registered CBT institutions was significantly associated with the number of patients who received CBT. CONCLUSIONS: The provision of CBT did not increase in the first 6 years (FY2010-2015) after its coverage in Japan's national health insurance scheme. Further studies including a questionnaire survey of registered CBT institutions are required to get more detailed information on the dissemination of CBT in Japan.

[Pharmacotherapy from the viewpoint of nursing: pharmacology education for nurses as a practitioner of medication].

The installation of nursing colleges/universities has rapidly increased from the late 1990s, there are 263 institutions in Japan as of 2018. Pharmacology and clinical pharmacology education in undergraduate and postgraduate nursing colleges/universities is highly important, in addition, the education of clinical pharmacology in the training courses of Certified Nurse Specialist, Certified Nurse and Nurse designated procedures is positioned as compulsory subject. Whereas, the lack of human resources involved in pharmacology education due to the rapid increase of nursing colleges/universities cannot be denied. Comprehensive pharmacology education in nursing based on the "Patient-oriented Pharmacology" is effective against the improvement of quality of pharmacotherapy and patient satisfaction. It is important to provide an opportunity to learn comprehensive education program of nursing pharmacology as a mutual cooperation between both fields of nursing sciences and pharmacology.

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.

Lysophosphatidic acid-LPA1 receptor-Rho-Rho kinase-induced up-regulation of Nav1.7 sodium channel mRNA and protein in adrenal chromaffin cells: enhancement of 22Na+ influx, 45Ca2+ influx and catecholamine secretion.

In cultured bovine adrenal chromaffin cells, chronic (> or = 24 h) treatment with lysophosphatidic acid (LPA) augmented veratridine-induced 22Na+ influx via Na(v)1.7 by approximately 22% (EC(50) = 1 nmol/L), without changing nicotine-induced 22Na+ influx via nicotinic receptor-associated channel. LPA enhanced veratridine (but not nicotine)-induced 45Ca2+ influx via voltage-dependent calcium channel and catecholamine secretion. LPA shifted concentration-response curve of veratridine for 22Na+ influx upward, without altering the EC(50) of veratridine. Ptychodiscus brevis toxin-3 allosterically enhanced veratridine-induced 22Na+ influx by twofold in non-treated and LPA-treated cells. Whole-cell patch-clamp analysis showed that peak Na+ current amplitude was greater by 39% in LPA (100 nmol/L for 36 h)-treated cells; however, I-V curve and steady-state inactivation/activation curves were comparable between non-treated and LPA-treated cells. LPA treatment (> or = 24 h) increased cell surface [3H]saxitoxin binding by approximately 28%, without altering the K(d) value; the increase was prevented by cycloheximide, actinomycin D, or Ki16425, dioctylglycerol pyrophosphate 8:0 (two inhibitors of LPA(1) and LPA3 receptors), or botulinum toxin C3 (Rho inhibitor), Y27632 (Rho kinase inhibitor), consistent with LPA(1) receptor expression in adrenal chromaffin cells. LPA raised Nav1.7 mRNA level by approximately 37%. Thus, LPA-LPA(1) receptor-Rho/Rho kinase pathway up-regulated cell surface Nav1.7 and Nav1.7 mRNA levels, enhancing veratridine-induced Ca2+ influx and catecholamine secretion.