"I'd have no idea how to go about this " - a survey of Australian medical students' perspectives on their men's health education.

BACKGROUND: While there have been calls over the last 15 years for the inclusion of training in sex and gender-based medicine in medical school curricula and to sustain such improvements through a more gender responsive health system, little progress has been made. A related objective of the Australian National Men's Health Strategy (2020-30) is to improve practitioner core learning competencies in men's health as a critical step to reducing the burden of disease in men and disparities between men in health care access and outcomes. The aim of this study was therefore to obtain Australian medical student perspectives on the extent to which men's health and sex and gender-based medicine education is delivered in their curricula, their preparedness for engaging with men in clinical practice, and the men's health content they would have found useful during their training. METHODS: Eighty-three students (48% male) from 17 accredited medical schools, and in at least their fourth year of training, completed an online survey. The survey was co-designed by a multidisciplinary team of men's health researchers and clinicians, alongside a student representative. A mix of quantitative and qualitative survey items inquired about students' preparedness for men's health clinical practice, and coverage of men's health and sex- and gender-based medicine in their curricula. RESULTS: Most students reported minimal to no men's health coverage in their medical school education (65%). While few were offered optional men's health units (10.5%), the majority would have liked more formal training on the topic (78%). Accompanying qualitative findings substantiated a lack of preparedness among medical students to engage male patients, likely stemming from minimal coverage of men's health in their medical education. CONCLUSIONS: Australian medical students may feel underprepared for contemporary men's health clinical practice, as well as, albeit to a lesser extent, women's health clinical practice. There is a clear need and desire amongst medical students to enhance curricula with sex and gender-based medicine training.

Suicidal ideation in men during COVID-19: an examination of protective factors.

BACKGROUND: Men account for three-quarters of all suicide deaths in many Western nations including Australia. Whilst extensive research has examined risk factors for suicidal ideation and behaviour in men, protective factors remain underexplored, particularly social support, resilience and coping behaviours. Such factors are important to examine particularly in the context of COVID-19, where enforced isolation (among other negative lifestyle effects) has created widespread risk for the development of suicidal ideation. This mixed-methods study aimed to examine associations of various protective factors with suicidal ideation in men, using data from an online survey conducted during the COVID-19 pandemic. In addition, we aimed to qualitatively investigate men's self-reported protective strategies when experiencing suicidal thoughts and behaviour. METHODS: A convenience sample of 700 men (age M = 50.3 years; SD = 15.2 years) responded to an online survey including quantitative measures of suicidal ideation, planning and attempt, alongside employment and relationship status, coping, social support, resilience, and a qualitative free-text item gauging men's self-reported protective strategies. Multinomial logistic regression was applied to compare odds of sub-categories of suicide risk (ideation; planning) according to protective factors. Qualitative responses were analysed via thematic analysis. RESULTS: Men in a relationship, and those lower in emotion-focused and avoidant coping reported lower odds of suicidal ideation. Maintaining employment throughout the pandemic was protective against suicidal ideation and planning; as was greater perceived social support from friends. Greater self-reported resilience was protective against suicidal ideation and planning. Qualitative analyses led to the development of two themes: coping and connecting, reflecting men's intra- and interpersonal management strategies; and sustaining selflessness, where men's imaginings of the collateral damage of their suicidal behaviour was protective against action on suicidal thoughts or plans. CONCLUSIONS: Findings of this study speak to the nuanced roles of interpersonal connections, resilience and coping behaviours in protecting against suicidal ideation and planning in men. In addition, qualitative insights further cement men's identification with familial protector and/or provider roles as protective against suicidal action.

A novel soluble complement receptor 1 fragment with enhanced therapeutic potential.

Human complement receptor 1 (HuCR1) is a pivotal regulator of complement activity, acting on all three complement pathways as a membrane-bound receptor of C3b/C4b, C3/C5 convertase decay accelerator, and cofactor for factor I-mediated cleavage of C3b and C4b. In this study, we sought to identify a minimal soluble fragment of HuCR1, which retains the complement regulatory activity of the wildtype protein. To this end, we generated recombinant, soluble, and truncated versions of HuCR1 and compared their ability to inhibit complement activation in vitro using multiple assays. A soluble form of HuCR1, truncated at amino acid 1392 and designated CSL040, was found to be a more potent inhibitor than all other truncation variants tested. CSL040 retained its affinity to both C3b and C4b as well as its cleavage and decay acceleration activity and was found to be stable under a range of buffer conditions. Pharmacokinetic studies in mice demonstrated that the level of sialylation is a major determinant of CSL040 clearance in vivo. CSL040 also showed an improved pharmacokinetic profile compared with the full extracellular domain of HuCR1. The in vivo effects of CSL040 on acute complement-mediated kidney damage were tested in an attenuated passive antiglomerular basement membrane antibody-induced glomerulonephritis model. In this model, CSL040 at 20 and 60 mg/kg significantly attenuated kidney damage at 24 h, with significant reductions in cellular infiltrates and urine albumin, consistent with protection from kidney damage. CSL040 thus represents a potential therapeutic candidate for the treatment of complement-mediated disorders.

Consuming a Protein and Fiber-Based Supplement Preload Promotes Weight Loss and Alters Metabolic Markers in Overweight Adults in a 12-Week, Randomized, Double-Blind, Placebo-Controlled Trial.

BACKGROUND: Higher protein and fiber diets promote weight management and metabolic health. OBJECTIVES: This study aimed to determine if greater weight loss and positive changes in metabolic outcomes could be achieved with twice-daily consumption of a high-protein and fiber-based multi-ingredient nutritional shake (HPF) compared with an isocaloric low-protein, lower fiber-based placebo (LPF). METHODS: Study procedures were conducted by an independent research organization under clinicaltrials.gov registration NCT03057873. Healthy overweight and obese adults [n = 206; BMI (kg/m2): 27-35; 70% female] were randomly assigned to HPF or LPF. All participants were prescribed an energy-restricted diet (500 kcal/d less than energy needs) and consumed a HPF (17 g protein, 6 g fiber) or LPF (1 g protein, 3 g fiber) shake 30 min before breakfast and lunch for 12 wk. Primary outcomes included body weight and total body fat percentage. Blood samples were collected at days (D) 0, 28, 56, and 84 for secondary analyses related to metabolic markers of health. RESULTS: Although weight loss occurred in both groups, HPF had greater weight loss at D84 compared with LPF (-3.3 kg vs. -1.8 kg, P < 0.05). Percentage body fat decreased in both groups (HPF: -1.33%, LPF: -1.09%; P < 0.001) with no differences between groups. Serum total cholesterol, LDL cholesterol, and oxidized LDL decreased between -5.1% to -8.3%, whereas adiponectin increased over time in both groups; these changes occurred to a greater extent in HPF compared with LPF (all P < 0.05). CONCLUSIONS: A multi-ingredient HPF nutritional supplement shake consumed as a preload before breakfast and lunch positively influenced weight management and metabolic outcomes in overweight adults compared with an LPF placebo. These findings suggest that specific nutrient factors (i.e., potentially including protein, fiber, and bioactive content) other than calorie reduction alone influence the success of a weight-loss regimen. This trial was registered at www.clinicaltrials.gov as NCT03057873.

Australian men's initial pathways into mental health services.

ISSUE ADDRESSED: Many men are challenged by barriers to mental health help-seeking and engagement. For men who do access care, their pathways to engaging services can offer important insights to what might constitute gender-specific care. METHODS: Data were drawn from an online cross-sectional survey of N = 2009 Australian men (aged 16-85; M = 43.5) reflecting on their initial pathways to mental health services, including their reasons for help-seeking, how they first located a therapist and the source of any initial recommendation for engaging with services. Respondents were recruited with targeted advertisements via Movember's Facebook page. RESULTS: A relatively even age distribution was observed, with most respondents residing in metropolitan areas (60.4%), a majority employed full time (47.7%), and 25.7% identifying as gay or bisexual. Participants tended to be self-motivated to seek help, with referrals by general practitioners to specialist mental health services. The most common underpinning precipitant for seeking help was anxiety, particularly for younger men, whereas older men tended to have sought help more commonly for familial, relationship or work-related factors. Older men were also more likely to report self-motivated help-seeking, whereas younger men more commonly sought help on the recommendation of a family member. CONCLUSIONS: There are varied pathways for men's initial mental health help-seeking journeys that require an ongoing examination to ensure health promotion efforts are appropriately tailored and responding to men's needs. SO WHAT: As more men access mental health services, having a nuanced understanding of their likely pathways to care can inform the help-seeking efforts of other men as well as guide improved services and systems to reduce barriers.

Haemopedia RNA-seq: a database of gene expression during haematopoiesis in mice and humans.

During haematopoiesis, haematopoietic stem cells differentiate into restricted potential progenitors before maturing into the many lineages required for oxygen transport, wound healing and immune response. We have updated Haemopedia, a database of gene-expression profiles from a broad spectrum of haematopoietic cells, to include RNA-seq gene-expression data from both mice and humans. The Haemopedia RNA-seq data set covers a wide range of lineages and progenitors, with 57 mouse blood cell types (flow sorted populations from healthy mice) and 12 human blood cell types. This data set has been made accessible for exploration and analysis, to researchers and clinicians with limited bioinformatics experience, on our online portal Haemosphere: https://www.haemosphere.org. Haemosphere also includes nine other publicly available high-quality data sets relevant to haematopoiesis. We have added the ability to compare gene expression across data sets and species by curating data sets with shared lineage designations or to view expression gene vs gene, with all plots available for download by the user.

Challenges working with men: Australian therapists' perspectives.

OBJECTIVE: Emerging research highlights that therapists experience difficulty engaging and retaining male clients in talk therapy. Understanding therapists' challenges when working with men can inform gender-specific training efforts. METHODS: Open-ended qualitative survey data were collected from a sample of 421 Australian-based therapists. Participants described that which they find most challenging about therapeutic work with men. Responses were analyzed using inductive thematic analysis. RESULTS: Three themes were revealed: (1) men's wavering commitment and engagement; (2) males as ill-equipped for therapy; and (3) therapists' uncertainty. Contrasting state and trait constructs, much of the men's state-based wavering commitment and engagement was positioned as amenable to change whereas traits assigned men as ill-equipped for therapy and unreachable. CONCLUSION: These findings underscore a clear need to better target training efforts to directly respond to the needs of therapists working with men, such that all therapists are well-equipped to meet men with gender-sensitive therapy.

Combining multiple tools outperforms individual methods in gene set enrichment analyses.

Motivation: Gene set enrichment (GSE) analysis allows researchers to efficiently extract biological insight from long lists of differentially expressed genes by interrogating them at a systems level. In recent years, there has been a proliferation of GSE analysis methods and hence it has become increasingly difficult for researchers to select an optimal GSE tool based on their particular dataset. Moreover, the majority of GSE analysis methods do not allow researchers to simultaneously compare gene set level results between multiple experimental conditions. Results: The ensemble of genes set enrichment analyses (EGSEA) is a method developed for RNA-sequencing data that combines results from twelve algorithms and calculates collective gene set scores to improve the biological relevance of the highest ranked gene sets. EGSEA's gene set database contains around 25 000 gene sets from sixteen collections. It has multiple visualization capabilities that allow researchers to view gene sets at various levels of granularity. EGSEA has been tested on simulated data and on a number of human and mouse datasets and, based on biologists' feedback, consistently outperforms the individual tools that have been combined. Our evaluation demonstrates the superiority of the ensemble approach for GSE analysis, and its utility to effectively and efficiently extrapolate biological functions and potential involvement in disease processes from lists of differentially regulated genes. Availability and Implementation: EGSEA is available as an R package at http://www.bioconductor.org/packages/EGSEA/ . The gene sets collections are available in the R package EGSEAdata from http://www.bioconductor.org/packages/EGSEAdata/ . Contacts: monther.alhamdoosh@csl.com.au mritchie@wehi.edu.au. Supplementary information: Supplementary data are available at Bioinformatics online.

Patient blood management in colorectal cancer patients: a survey among Dutch gastroenterologists, surgeons, and anesthesiologists.

INTRODUCTION: There is an increasing awareness to integrate patient blood management (PBM) within routine surgical care. Limited information about the implementation of PBM in colorectal cancer surgery is available. This is curious, as preoperative anemia, associated with increased morbidity, is highly prevalent in colorectal cancer patients. Present study aimed to assess the current PBM strategies in the Netherlands. METHODS: An online electronic survey was developed and sent to surgeons of the Dutch Taskforce Coloproctology (177 in total). In addition, for each hospital in which surgery for colorectal cancer surgery is performed (75 in total), the survey was sent to one gastroenterologist and one anesthesiologist. Analyses were performed using descriptive statistics. RESULTS: A total of 192 physicians responded to the survey (response rate 58.7%). In 73 hospitals (97.3%) the survey was conducted by at least one physician. Regarding the management of a mild-moderate preoperative anemia, no clear policy was reported in half of the hospitals (49.3%). In 38.7% of the hospitals, iron status was indicated to be measured during screening for colorectal cancer. In addition, in only 13.3% of the hospitals, iron status was measured by the anesthesiologist during preoperative assessment. CONCLUSION: The Present study shows a distinct variability in PBM practices in colorectal cancer care. Strikingly, this variability was not only seen between, but also within Dutch hospitals, demonstrated by often variable responses from physicians from the same institution. As a result, the present study clearly demonstrates the lack of consensus on PBM, resulting in a suboptimal preoperative blood management strategy.

Therapeutic Targeting of the G-CSF Receptor Reduces Neutrophil Trafficking and Joint Inflammation in Antibody-Mediated Inflammatory Arthritis.

G-CSF is a hemopoietic growth factor that has a role in steady state granulopoiesis, as well as in mature neutrophil activation and function. G-CSF- and G-CSF receptor-deficient mice are profoundly protected in several models of rheumatoid arthritis, and Ab blockade of G-CSF also protects against disease. To further investigate the actions of blocking G-CSF/G-CSF receptor signaling in inflammatory disease, and as a prelude to human studies of the same approach, we developed a neutralizing mAb to the murine G-CSF receptor, which potently antagonizes binding of murine G-CSF and thereby inhibits STAT3 phosphorylation and G-CSF receptor signaling. Anti-G-CSF receptor rapidly halted the progression of established disease in collagen Ab-induced arthritis in mice. Neutrophil accumulation in joints was inhibited, without rendering animals neutropenic, suggesting an effect of G-CSF receptor blockade on neutrophil homing to inflammatory sites. Consistent with this, neutrophils in the blood and arthritic joints of anti-G-CSF receptor-treated mice showed alterations in cell adhesion receptors, with reduced CXCR2 and increased CD62L expression. Furthermore, blocking neutrophil trafficking with anti-G-CSF receptor suppressed local production of proinflammatory cytokines (IL-1ß, IL-6) and chemokines (KC, MCP-1) known to drive tissue damage. Differential gene expression analysis of joint neutrophils showed a switch away from an inflammatory phenotype following anti-G-CSF receptor therapy in collagen Ab-induced arthritis. Importantly, G-CSF receptor blockade did not adversely affect viral clearance during influenza infection in mice. To our knowledge, we describe for the first time the effect of G-CSF receptor blockade in a therapeutic model of inflammatory joint disease and provide support for pursuing this therapeutic approach in treating neutrophil-associated inflammatory diseases.

Matrix metalloproteinase and heparin-stimulated serine proteinase activities in post-prostate massage urine of men with prostate cancer.

Proteinases secreted by the prostate gland have a reproductive function in cleaving proteins in the ejaculate and in the female reproductive tract, but some may have a fundamental role in disease and pathological processes including cancer. The purpose of this study was to determine if there were differences in proteinase activities in urine samples collected following prostate massage of men positive (CaP) or negative (no evidence of malignancy, NEM) for biopsy determined prostate cancer. Matrix metalloproteinase (MMP) and serine proteinase activities were detected using protein substrate zymography. There were no differences in activities of MMP-2, proMMP-9, and MMP-9/NGAL (neutrophil gelatinase associated lipocalin) complex (gelatin substrate) in men with detected prostate cancer, although the latter two were somewhat diminished. A caseinolytic activity of about 75kDa inhibited by calcium did not differ between the NEM and CaP groups. Heparin stimulated calcium sensitive gelatinolytic activities of approximately 22, 42, and 60kDa, but did not affect activities of MMP-2, MMP-9, or the 75kDa caseinolytic activity. The 22, 42, and 60kDa activities appear to be serine proteinases since they were inhibited by benzamidine. There was a significant decrease in the 22kDa heparin-stimulated serine proteinase activity in urines of men with cancer. Proteinase expression and activities, perhaps in combination with other potential markers, may prove useful in urine for detection and evaluation of prostate cancer.

One-step zero-background IgG reformatting of phage-displayed antibody fragments enabling rapid and high-throughput lead identification.

We describe a novel cloning method, referred to as insert-tagged (InTag) positive selection, for the rapid one-step reformatting of phage-displayed antibody fragments to full-length immunoglobulin Gs (IgGs). InTag positive selection enables recombinant clones of interest to be directly selected without cloning background, bypassing the laborious process of plating out cultures and colony screening and enabling the cloning procedure to be automated and performed in a high-throughput format. This removes a significant bottleneck in the functional screening of phage-derived antibody candidates and enables a large number of clones to be directly reformatted into IgG without the intermediate step of Escherichia coli expression and testing of soluble antibody fragments. The use of InTag positive selection with the Dyax Fab-on-phage antibody library is demonstrated, and optimized methods for the small-scale transient expression of IgGs at high levels are described. InTag positive selection cloning has the potential for wide application in high-throughput DNA cloning involving multiple inserts, markedly improving the speed and quality of selections from protein libraries.

Neurocognitive and psychiatric dimensions of hot, but not cool, impulsivity predict HIV sexual risk behaviors among drug users in protracted abstinence.

BACKGROUND: Impulsivity is an important risk factor for HIV risky drug and sexual behaviors. Research identifies hot (i.e. affectively-mediated, reward-based) and cool (motoric, attentional, independent of context) neurocognitive and psychiatric dimensions of impulsivity, though the impact of specific drugs of abuse on these varieties of impulsivity remains an open question. OBJECTIVES: The present study examined the associations of neurocognitive and psychiatric varieties of hot and cool impulsivity with measures of lifetime and recent sexual risk behaviors among users of different classes of drugs. METHODS: The study sample was comprised of drug users in protracted (> 1 year) abstinence: heroin mono-dependent (n = 61), amphetamine mono-dependent (n = 44), and polysubstance dependent (n = 73). Hot impulsivity was operationalized via neurocognitive tasks of reward-based decision-making and symptoms of psychopathy. Cool impulsivity was operationalized via neurocognitive tasks of response inhibition and symptoms of attention deficit/hyperactivity disorder (ADHD). RESULTS: Hot impulsivity was associated with sexual risk behaviors among heroin and amphetamine users in protracted abstinence, whereas cool impulsivity was not associated with sexual risk behaviors among any drug-using group. Neurocognitive hot impulsivity was associated with recent (past 30-day) sexual risk behaviors, whereas psychopathy was associated with sexual risk behaviors during more remote time-periods (past 6 month and lifetime) and mediated the association between heroin dependence and past 6-month sexual risk behaviors. CONCLUSION: Assessments and interventions aimed at reducing sexual risk behaviors among drug users should focus on hot neurocognitive and psychiatric dimensions of impulsivity, such as decision-making and psychopathy. Cool dimensions of impulsivity such as response inhibition and ADHD were not related to sexual risk behaviors among drug users in protracted abstinence.

Dual-Functions of miR-373 and miR-520c by Differently Regulating the Activities of MMP2 and MMP9.

MicroRNA-520c (miR-520c) and microRNA-373 (miR-373) are originally characterized as both oncogenes and tumor suppressors in different types of human cancers. In this study, we found that translation of mRNA of MT1-MMP, an oncogene related to tumor metastasis, was well inhibited by miR-520c and miR-373 in several types of human cancer cells. Our experimental data demonstrated that these two microRNAs inhibited the translation of mRNA of MT1-MMP and down-regulated its proteolytic enzyme activities via targeting 3'UTR of mRNA of MT1-MMP, further decreased activating proMMP2 into active MMP2 in fibrosarcoma HT1080, benign prostatic hyperplasia epithelial cell BPH-1 and glioblastoma U87GM. More interestingly, from the effects of microRNAs on cell functions, we found that cell growth were all blocked on fibronectin and type IV collagen coated plates and also in three-dimension type I collagen lattice but enhanced only in HT1080 cells on type IV collagen coated plates and in three-dimension type I collagen lattice; cell migration results showed the same effect as that of cell growth. The difference was due to up-regulating the expression of MMP9 gene by miR-520c and miR-373 in HT1080 cells but not in BPH-1 and U87GM cells. Our findings suggest that miR-520c and miR-373, which have different roles in different type of cancer via regulating the translation of mRNA of MT1-MMP and the expression of MMP9 gene, might have an important clue on clinic when selecting the therapeutic regimen and finding new drugs for intervention in different kinds of cancer.

Α- and ß-subunit composition of voltage-gated sodium channels investigated with µ-conotoxins and the recently discovered µO§-conotoxin GVIIJ.

We investigated the identities of the isoforms of the α (NaV1)- and ß (NaVß)-subunits of voltage-gated sodium channels, including those responsible for action potentials in rodent sciatic nerves. To examine α-subunits, we used seven µ-conotoxins, which target site 1 of the channel. With the use of exogenously expressed channels, we show that two of the µ-conotoxins, µ-BuIIIB and µ-SxIIIA, are 50-fold more potent in blocking NaV1.6 from mouse than that from rat. Furthermore, we observed that µ-BuIIIB and µ-SxIIIA are potent blockers of large, myelinated A-fiber compound action potentials (A-CAPs) [but not small, unmyelinated C-fiber CAPs (C-CAPs)] in the sciatic nerve of the mouse (unlike A-CAPs of the rat, previously shown to be insensitive to these toxins). To investigate ß-subunits, we used two synthetic derivatives of the recently discovered µO§-conotoxin GVIIJ that define site 8 of the channel, as previously characterized with cloned rat NaV1- and NaVß-subunits expressed in Xenopus laevis oocytes, where it was shown that µO§-GVIIJ is a potent inhibitor of several NaV1-isoforms and that coexpression of NaVß2 or -ß4 (but not NaVß1 or -ß3) totally protects against block by µO§-GVIIJ. We report here the effects of µO§-GVIIJ on 1) sodium currents of mouse NaV1.6 coexpressed with various combinations of NaVß-subunits in oocytes; 2) A- and C-CAPs of mouse and rat sciatic nerves; and 3) sodium currents of small and large neurons dissociated from rat dorsal root ganglia. Our overall results lead us to conclude that action potentials in A-fibers of the rodent sciatic nerve are mediated primarily by NaV1.6 associated with NaVß2 or NaVß4.

Induction of a heparin-stimulated serine proteinase in sex accessory gland tumors of the Lobund-Wistar rat.

Induction of new proteinase activities that may process growth factors, modify cell surface receptors, cleave extracellular matrix proteins, etc. is considered fundamental in carcinogenesis. The purpose of this study was to characterize a novel proteinase activity induced in sex accessory gland cancers (about 70% in seminal vesicles) of adult male Lobund-Wistar rats by a single injection of N-nitroso-N-methylurea (NMU; 25mg/kg) followed by implanted testosterone propionate (45mg in silastic tubing every 2months) treatment for 10-14months. A 28kDa proteinase activity was detected in tumor extracts using SDS-gelatin gel zymography with incubations done without CaCl2. Its activity was stimulated 15 fold by heparin (optimal activity 1.5-3.0µg/lane) added to the tissue extract-SDS sample buffer prior to electrophoresis. No 28kDa heparin-stimulated proteinase (H-SP) was found in the dorsal, lateral and anterior (coagulating gland) prostate lobes or seminal vesicles of untreated adult rats, but there was a 26-30kDa Ca(2+)-independent proteinase activity in the ventral prostate that showed limited heparin stimulation. The 28kDa H-SP was completely inhibited by 1.0mM 4-(2-aminoethyl)benzenesulfonylfluoride (AESBF) indicating that it was a serine-type proteinase. Other types of proteinase inhibitors were without effect, including serine proteinase inhibitors benzamidine, tranexamic acid and ε-aminocaproic acid. Proteinase activities of about 28kDa were found with casein, fibrinogen or carboxymethylated transferrin as substrate, however, these activities were not stimulated by heparin. Similar levels of activities of the 28kDa H-SP were found in primary tumors and their metastases, but little/no activity was detected in serum, even from rats with large tumor volume and metastases. These data demonstrate overexpression of a heparin-stimulated 28kDa serine proteinase in the primary tumors of sex accessory gland cancers and their metastases. This proteinase either does not leak into or is inactivated in the blood. The role of this proteinase remains to be determined, but its possible interaction with extracellular glycosaminoglycans could focus its proteolytic activity in the tumor microenvironment and affect tumor growth.

µ-Conotoxins that differentially block sodium channels NaV1.1 through 1.8 identify those responsible for action potentials in sciatic nerve.

Voltage-gated sodium channels (VGSCs) are important for action potentials. There are seven major isoforms of the pore-forming and gate-bearing α-subunit (Na(V)1) of VGSCs in mammalian neurons, and a given neuron can express more than one isoform. Five of the neuronal isoforms, Na(V)1.1, 1.2, 1.3, 1.6, and 1.7, are exquisitely sensitive to tetrodotoxin (TTX), and a functional differentiation of these presents a serious challenge. Here, we examined a panel of 11 µ-conopeptides for their ability to block rodent Na(V)1.1 through 1.8 expressed in Xenopus oocytes. Although none blocked Na(V)1.8, a TTX-resistant isoform, the resulting "activity matrix" revealed that the panel could readily discriminate between the members of all pair-wise combinations of the tested isoforms. To examine the identities of endogenous VGSCs, a subset of the panel was tested on A- and C-compound action potentials recorded from isolated preparations of rat sciatic nerve. The results show that the major subtypes in the corresponding A- and C-fibers were Na(V)1.6 and 1.7, respectively. Ruled out as major players in both fiber types were Na(V)1.1, 1.2, and 1.3. These results are consistent with immunohistochemical findings of others. To our awareness this is the first report describing a qualitative pharmacological survey of TTX-sensitive Na(V)1 isoforms responsible for propagating action potentials in peripheral nerve. The panel of µ-conopeptides should be useful in identifying the functional contributions of Na(V)1 isoforms in other preparations.