Pycallingcards: an integrated environment for visualizing, analyzing, and interpreting Calling Cards data.

MOTIVATION: Unraveling the transcriptional programs that control how cells divide, differentiate, and respond to their environments requires a precise understanding of transcription factors' (TFs) DNA-binding activities. Calling cards (CC) technology uses transposons to capture transient TF binding events at one instant in time and then read them out at a later time. This methodology can also be used to simultaneously measure TF binding and mRNA expression from single-cell CC and to record and integrate TF binding events across time in any cell type of interest without the need for purification. Despite these advantages, there has been a lack of dedicated bioinformatics tools for the detailed analysis of CC data. RESULTS: We introduce Pycallingcards, a comprehensive Python module specifically designed for the analysis of single-cell and bulk CC data across multiple species. Pycallingcards introduces two innovative peak callers, CCcaller and MACCs, enhancing the accuracy and speed of pinpointing TF binding sites from CC data. Pycallingcards offers a fully integrated environment for data visualization, motif finding, and comparative analysis with RNA-seq and ChIP-seq datasets. To illustrate its practical application, we have reanalyzed previously published mouse cortex and glioblastoma datasets. This analysis revealed novel cell-type-specific binding sites and potential sex-linked TF regulators, furthering our understanding of TF binding and gene expression relationships. Thus, Pycallingcards, with its user-friendly design and seamless interface with the Python data science ecosystem, stands as a critical tool for advancing the analysis of TF functions via CC data. AVAILABILITY AND IMPLEMENTATION: Pycallingcards can be accessed on the GitHub repository: https://github.com/The-Mitra-Lab/pycallingcards.

Long noncoding RNA GATA2-AS1 augments endothelial hypoxia inducible factor 1-α induction and regulates hypoxic signaling.

Vascular endothelial cells form the inner cellular lining of blood vessels and have myriad physiologic functions including angiogenesis and response to hypoxia. We recently identified a set of endothelial cell (EC)-enriched long noncoding RNAs (lncRNAs) in differentiated human primary cell types and described the role of the STEEL lncRNA in angiogenic patterning. We sought to further understand the role of EC-enriched lncRNAs in physiologic adaptation of the vascular endothelium. In this work, we describe an abundant, cytoplasmic, and EC-enriched lncRNA, GATA2-AS1, that is divergently transcribed from the EC-enriched developmental regulator, GATA2. While GATA2-AS1 is largely coexpressed with GATA2 in ECs, GATA2-AS1 and GATA2 appear to be complementary rather than synergistic as they have mostly distinct target genes. Common single nucleotide variants in GATA2-AS1 exons are associated with early-onset coronary artery disease and decreased expression of GATA2-AS1 in endothelial cell lines. In most cells, HIF1-α is central to the transcriptional response to hypoxia, while in ECs, both HIF1-α and HIF2-α are required to coordinate an acute and chronic response, respectively. In this setting, GATA2-AS1 contributes to the "HIF switch" and augments HIF1-α induction in acute hypoxia to regulate HIF1-α/HIF2-α balance. In hypoxia, GATA2-AS1 orchestrates HIF1-α-dependent induction of the glycolytic pathway and HIF1-α-independent maintenance of mitochondrial biogenesis. Similarly, GATA2-AS1 coordinates both metabolism and "tip/stalk" cell signaling to regulate angiogenesis in hypoxic ECs. Furthermore, we find that GATA2-AS1 expression patterns are perturbed in atherosclerotic disease. Together, these results define a role for GATA2-AS1 in the EC-specific response to hypoxia.

Fragility of statistically significant outcomes in randomized trials comparing bariatric surgeries.

BACKGROUND: Randomized controlled trials (RCTs) are regarded as high-level evidence, but the strength of their P values can be difficult to ascertain. The Fragility Index (FI) is a novel metric that evaluates the frailty of trial findings. It is defined as the minimum number of patients required to change from a non-event to event for the findings to lose statistical significance. This study aims to characterize the robustness of bariatric surgery RCTs by examining their FIs. METHODS: A search was conducted in MEDLINE, EMBASE, and CENTRAL from January 2000 to February 2022 for RCTs comparing two bariatric surgeries with statistically significant dichotomous outcomes. Bivariate correlation was conducted to identify associations between FI and trial characteristics. RESULTS: A total of 35 RCTs were included with a median sample size of 80 patients (Interquartile range [IQR] 58-109). The median FI was 2 (IQR 0-5), indicating that altering the status of two patients in one treatment arm would overturn the statistical significance of results. Subgroup analyses of RCTs evaluating diabetes-related outcomes produced a FI of 4 (IQR 2-6.5), while RCTs comparing Roux-en-Y gastric bypass and sleeve gastrectomy had an FI of 2 (IQR 0.5-5). Increasing FI was found to be correlated with decreasing P value, increasing sample size, increasing number of events, and increasing journal impact factor. CONCLUSION: Bariatric surgery RCTs are fragile, with only a few patients required to change from non-events to events to reverse the statistical significance of most trials. Future research should examine the use of FI in trial design.

Fragility of statistically significant findings from randomized trials in comparing laparoscopic versus robotic abdominopelvic surgeries.

BACKGROUND: Utility of robotic over laparoscopic approach has been an area of debate across all surgical specialties over the past decade. The fragility index (FI) is a metric that evaluates the frailty of randomized controlled trials (RCTs) findings by altering the status of patients from an event to non-event until significance is lost. This study aims to evaluate the robustness of RCTs comparing laparoscopic and robotic abdominopelvic surgeries through the FI. METHODS: A search was conducted in MEDLINE and EMBASE for RCTs with dichotomous outcomes comparing laparoscopic and robot-assisted surgery in general surgery, gynecology, and urology. The FI and reverse fragility Index (RFI) metrics were used to assess the strength of findings reported by RCTs, and bivariate correlation was conducted to analyze relationships between FI and trial characteristics. RESULTS: A total of 21 RCTs were included, with a median sample size of 89 participants (Interquartile range [IQR] 62-126). The median FI was 2 (IQR 0-15) and median RFI 5.5 (IQR 4-8.5). The median FI was 3 (IQR 1-15) for general surgery (n = 7), 2 (0.5-3.5) for gynecology (n = 4), and 0 (IQR 0-8.5) for urology RCTs (n = 4). Correlation was found between increasing FI and decreasing p-value, but not sample size, number of outcome events, journal impact factor, loss to follow-up, or risk of bias. CONCLUSION: RCTs comparing laparoscopic and robotic abdominal surgery did not prove to be very robust. While possible advantages of robotic surgery may be emphasized, it remains novel and requires further concrete RCT data.

Epigenetic Heterogeneity and Mitotic Heritability Prime Endothelial Cell Gene Induction.

Homogeneous populations of mature differentiated primary cell types can display variable responsiveness to extracellular stimuli, although little is known about the underlying mechanisms that govern such heterogeneity at the level of gene expression. In this article, we show that morphologically homogenous human endothelial cells exhibit heterogeneous expression of VCAM1 after TNF-α stimulation. Variability in VCAM1 expression was not due to stochasticity of intracellular signal transduction but rather to preexisting established heterogeneous states of promoter DNA methylation that were generationally conserved through mitosis. Variability in DNA methylation of the VCAM1 promoter resulted in graded RelA/p65 and RNA polymerase II binding that gave rise to a distribution of VCAM1 transcription in the population after TNF-α stimulation. Microarray analysis and single-cell RNA sequencing revealed that a number of cytokine-inducible genes shared this heterogeneous response pattern. These results show that heritable epigenetic heterogeneity is fundamental in inflammatory signaling and highlight VCAM1 as a metastable epiallele.

Gut Microbiota Influences Neuropathic Pain Through Modulating Proinflammatory and Anti-inflammatory T Cells.

BACKGROUND: Gut microbiota, a consortium of diverse microorganisms residing in the gastrointestinal tract, has emerged as a key player in neuroinflammatory responses, supporting the functional relevance of the "gut-brain axis." Chronic-constriction injury of the sciatic nerve (CCI) is a commonly used animal model of neuropathic pain with a major input from T cell-mediated immune responses. In this article, we sought to examine whether gut microbiota influences CCI neuropathic pain, and, if so, whether T-cell immune responses are implicated. METHODS: We used a mixture of wide-spectrum oral antibiotics to perturbate gut microbiota in mice and then performed CCI in these animals. Nociceptive behaviors, including mechanical allodynia and thermal hyperalgesia, were examined before and after CCI. Additionally, we characterized the spinal cord infiltrating T cells by examining interferon (IFN)-γ, interleukin (IL)-17, and Foxp3. Using a Foxp3-GFP-DTR "knock-in" mouse model that allows punctual depletion of regulatory T cells, we interrogated the role of these cells in mediating the effects of gut microbiota in the context of CCI neuropathic pain. RESULTS: We found that oral antibiotics induced gut microbiota changes and attenuated the development of CCI neuropathic pain, as demonstrated by dampened mechanical allodynia and thermal hyperalgesia. Percentages of IFN-γ-producing Th1 cells and Foxp3+ regulatory T cells were significantly different between animals that received oral antibiotics (Th1 mean = 1.0, 95% confidence interval [CI], 0.9-1.2; Foxp3 mean = 8.1, 95% CI, 6.8-9.3) and those that received regular water (Th1 mean = 8.4, 95% CI, 7.8-9.0, P < .01 oral antibiotics versus water, Cohen's d = 18.8; Foxp 3 mean = 2.8, 95% CI, 2.2-3.3, P < .01 oral antibiotics versus water, Cohen's d = 6.2). These T cells characterized a skewing from a proinflammatory to an anti-inflammatory immune profile induced by gut microbiota changes. Moreover, we depleted Foxp3+ regulatory T cells and found that their depletion reversed the protection of neuropathic pain mediated by gut microbiota changes, along with a dramatic increase of IFN-γ-producing Th1 cell infiltration in the spinal cord (before depletion mean = 2.8%, 95% CI, 2.2-3.5; after depletion mean = 9.1%, 95% CI, 7.2-11.0, p < .01 before versus after, Cohen's d = 5.0). CONCLUSIONS: Gut microbiota plays a critical role in CCI neuropathic pain. This role is mediated, in part, through modulating proinflammatory and anti-inflammatory T cells.

Enzalutamide with androgen deprivation therapy in Japanese men with metastatic hormone-sensitive prostate cancer: A subgroup analysis of the phase III ARCHES study.

OBJECTIVE: To evaluate the efficacy and safety of enzalutamide plus androgen deprivation therapy in Japanese men with metastatic hormone-sensitive prostate cancer. METHODS: A post-hoc analysis of the Japanese subgroup in the phase III, randomized, multinational ARCHES study (NCT02677896) was carried out. Patients with metastatic hormone-sensitive prostate cancer were randomized to receive enzalutamide or a placebo, plus androgen deprivation therapy, stratified by disease volume and prior docetaxel therapy. The primary end-point was radiographic progression-free survival. Secondary end-points included time to prostate-specific antigen progression and overall survival. RESULTS: Of 1150 patients, 92 Japanese patients were randomized to enzalutamide (n = 36) or a placebo (n = 56), plus androgen deprivation therapy; none received prior docetaxel. Enzalutamide plus androgen deprivation therapy reduced the risk of radiographic progression or death in Japanese patients by 61% versus the placebo, similar to the overall population. Similar results were observed with secondary end-points, showing clinical benefit of enzalutamide plus androgen deprivation therapy in Japanese patients. Overall survival data were immature. Grade 3-4 adverse events were reported in 47% and 25% of the enzalutamide and placebo groups, respectively. Nasopharyngitis, hypertension and abnormal hepatic function were reported more frequently in Japanese patients versus the overall population. CONCLUSIONS: Enzalutamide plus androgen deprivation therapy has clinical benefit with a tolerable safety profile in Japanese men with metastatic hormone-sensitive prostate cancer, consistent with the overall population.

Work Requirements and Medicaid Disenrollment in Arkansas, Kentucky, Louisiana, and Texas, 2018.

Objectives. To identify risk factors for Medicaid disenrollment after the implementation of Arkansas's work requirements.Methods. Using a 2018 telephone survey of 1208 low-income adults aged 30 to 49 years in Arkansas (expansion state with work requirements implemented in June 2018), Kentucky (expansion state with proposed work requirements blocked by courts), Louisiana (expansion state without work requirements), and Texas (nonexpansion state), we assessed Medicaid disenrollment rates among the age group targeted by Arkansas's policy.Results. The Medicaid disenrollment rate was highest in Texas (12.8%), followed by Arkansas (10.5%), Kentucky (5.8%), and Louisiana (2.8%). Over half of those who disenrolled in Texas and Arkansas became uninsured, compared with less than a quarter in Kentucky and Louisiana. In multivariate models, Arkansas had significantly higher disenrollment compared with the 3 comparison states; men and non-Hispanic Whites experienced higher disenrollment than women and racial minorities. In Arkansas, having a chronic condition was associated with higher disenrollment.Conclusions. As states debate work requirements and Medicaid reforms, our findings provide insights for policymakers about which populations may be most vulnerable to losing Medicaid coverage.

Analgesic Effects Evoked by Real and Imagined Acupuncture: A Neuroimaging Study.

Acupuncture can provide therapeutic analgesic benefits but is limited by its cost and scheduling difficulties. Guided imagery is a commonly used method for treating many disorders, such as chronic pain. The present study examined a novel intervention for pain relief that integrates acupuncture with imagery called video-guided acupuncture imagery treatment (VGAIT). A total of 27 healthy subjects were recruited for a crossover-design study that included 5 sessions administered in a randomized order (i.e., baseline and 4 different interventions). We investigated changes in pain threshold and fMRI signals modulated by: 1) VGAIT, watching a video of acupuncture previously administered on the participant's own body at baseline while imagining it being concurrently applied; 2) a VGAIT control condition, watching a video of a cotton swab touching the skin; 3) real acupuncture; and 4) sham acupuncture. Results demonstrated that real acupuncture and VGAIT significantly increased pain threshold compared with respective control groups. Imaging showed that real acupuncture produced greater activation of the insula compared with VGAIT. VGAIT produced greater deactivation at the rostral anterior cingulate cortex. Our findings demonstrate that VGAIT holds potential clinical value for pain management.

Methylphenidate and Morphine Combination Therapy in a Rat Model of Chronic Pain.

BACKGROUND: The incremental dose of opioids used in chronic pain management often leads to a reduced opioid analgesic effect, opioid misuse, and addiction. Central dopamine (DA) dysfunction contributes to the chronicity of pain and a decreased opioid analgesic effect. Methylphenidate (MPH/Ritalin) enhances central DA function by inhibiting DA reuptake. In this study, we used a rat model of chronic pain to examine whether combination of MPH with morphine (MOR) would improve the MOR analgesic effect under a chronic pain condition. METHODS: Tibiotarsal joint Complete Freund's Adjuvant (CFA) injection in rats was utilized to induce chronic nociception. The analgesic effect of low-dose MPH (0.25 mg/kg), low-dose MOR (2.5 mg/kg), and their combination was examined in CFA rats. Nociceptive behavior was assessed by von Frey test. Conditioned place preference (CPP) and open field tests (OFTs) were used to examine the rewarding behavior and locomotor activity in rats, respectively. RESULTS: Our findings are as follows: (1) in CFA rats with chronic pain, 2.5 mg/kg of MOR had less analgesic effect than 10 mg/kg of MOR at 28 days after injury (95% confidence intervals [CIs] for difference of means of von Frey threshold in gram: -11.9 [-6.5 to -17.3]); (2) in the 1-hour time window of 30-90 minutes after injection, the combination of MPH (0.25 mg/kg) with MOR (2.5 mg/kg) increased synergistically and prolonged the analgesic effect in CFA rats as compared with MPH or MOR alone (P = .01 for MPH by MOR interaction, and 95% CIs for difference of means of von Frey threshold in gram: 3.3 [1.37-6.12] for the combination versus MPH and 3.2 [1.35-5.74] for the combination versus MOR); (3) at the low dose (0.25 mg/kg), MPH did not increase locomotor activity (MOR + MPH versus MOR, P = .13) nor significantly enhanced MOR reward behavior (MOR + MPH versus MOR, P = .63) in CFA rats. CONCLUSIONS: Our data suggest that a combination therapy using low-dose MPH and MOR may produce a MOR-sparing effect in chronic pain management.

Persistent Nociception Facilitates the Extinction of Morphine-Induced Conditioned Place Preference.

BACKGROUND: As opioid abuse and addiction have developed into a major national health crisis, prescription of opioids for pain management has become more controversial. However, opioids do help some patients by providing pain relief and improving the quality of life. To better understand the addictive properties of opioids under chronic pain conditions, we used a conditioned place preference (CPP) paradigm to examine the rewarding properties of morphine in rats with persistent nociception. METHODS: Spared nerve injury (SNI) model was used to induce persistent nociception in rats. Nociceptive behavior was assessed by von Frey test. CPP test was used to examine the rewarding properties of morphine. RESULTS: Our findings are as follows: (1) SNI rats did not show a difference compared with sham rats in magnitude of morphine-induced CPP 1 day after last morphine injection (2-way analysis of variance; for SNI versus sham, F[1,42] = 0.014, P = .91; and 95% confidence intervals for difference of means, -5.9 [-58 to 46], 0.76 [-51 to 53], and 0.90 [-51 to 53] for 2.5, 5, and 10 mg/kg, respectively); (2) increasing morphine dosage (2.5, 5, and 10 mg/kg) did not further increase the magnitude of CPP in both sham and SNI rats (for dosage: F[2,42] = 0.94, P = .40); and (3) morphine-induced CPP persisted in sham rats but extinguished in SNI rats when tested at 8 days after last morphine injection (for sham versus SNI: Bonferroni correction, P < .006 for both 5 and 10 mg/kg doses; and 95% confidence intervals for difference of means, 80.3 [19.7-141] and 87.0 [26.3-148] for 5 and 10 mg/kg, respectively). CONCLUSIONS: Our data provide new evidence supporting the notion that the brain's reward circuitry changes in the context of persistent pain. This observational study suggests that future investigation into the neurobiology of opioid reward requires consideration of the circumstances in which opioid analgesics are administered.

Relationships Between Opioid Dosing, Pain Severity, and Disability in a Community-Based Chronic Pain Population: An Exploratory Retrospective Analysis.

OBJECTIVE: To determine the relationship between opioid dose change, pain severity, and function in patients with chronic pain. DESIGN: Retrospective cohort study. SETTING: Community interdisciplinary pain management practice. SUBJECTS: A total of 778 patients with chronic pain prescribed opioids for three or more consecutive months between April 1, 2013, and March 1, 2015. METHODS: Changes in opioid dose, pain severity rating, modified Roland Morris Disability Questionnaire score, and opioid risk data were extracted from medical records and analyzed for associations. RESULTS: Two hundred forty-three subjects (31.2%) had an overall dose decrease, 223 (28.7%) had a dose increase, and 312 (40.1%) had no significant change in dose (<20% change). There was a weak negative correlation between change in opioid dose and change in pain severity (r = -0.08, P = 0.04) but no association between change in disability scores and dose change (N = 526, P = 0.13). There was a weak positive correlation between change in pain severity rating and change in disability scores (r = 0.16, P < 0.001). CONCLUSIONS: The results suggest that escalating opioid doses may not necessarily result in clinically significant improvement of pain or disability. Similarly, significant opioid dose reductions may not necessarily result in worsened pain or disability. This exploratory investigation raised questions of possible subgroups of patients who might demonstrate improvement of pain and disability with opioid dose adjustments, and further research should prospectively explore this potential, given the limitations inherent in retrospective analyses. Prescribers should still consider reduction of opioid doses as recommended by current guidelines, in an effort to mitigate the potential risks associated with high-dose treatment.

Severe and near-fatal anaphylactic reactions triggered by chlorhexidine-coated catheters in patients undergoing renal allograft surgery: a case series.

PURPOSE: Although intraoperative anaphylaxis during surgery is a rare event, we describe five patients who experienced perioperative anaphylactic reactions during renal transplantation and were referred for investigation. CLINICAL FEATURES: Skin-prick and intradermal skin tests were done to investigate potential allergies to drugs given perioperatively prior to the development of anaphylaxis, including basiliximab, propofol, cefazolin, cis-atracurium, fentanyl, latex, remifentanil, and chlorhexidine. In addition, in vitro serologic testing for specific IgE was done in patients suspected to have had chlorhexidine anaphylaxis. All five patients were male, with a mean age of 48 yr (range 30-69). Skin testing for all drugs was non-reactive except for chlorhexidine, which was positive in four of five patients (one patient refused intradermal testing). In vitro test results for chlorhexidine-specific IgE were positive in all of the patients. Anesthetic records showed that intraoperative anaphylaxis had occurred immediately after insertion of a chlorhexidine-coated central venous catheter. CONCLUSIONS: Intraoperative insertion of chlorhexidine-coated central venous catheters can trigger life-threatening anaphylaxis in susceptible patients undergoing renal transplantation.

Estrogen-regulated miRNA-27b is altered by bisphenol A in human endometrial stromal cells.

MicroRNAs (miRs) are small molecules important for regulation of transcription and translation. The objective was to identify hormonally regulated miRs in human endometrial stromal cells and to determine the impact of the endocrine disruptor, bisphenol A (BPA), on those miRs. miR microarray analysis and multiple confirmatory cell preparations treated with 17ß-estradiol (E2) and BPA altered miR-27b, let-7c, let-7e and miR-181b. Further, decidualization downregulated miR-27b. VEGFB and VEGFC were validated as targets of miR-27b. Identification of miR-27b target genes suggests that BPA and E2 downregulate miR-27b thereby leading to upregulation of genes important for vascularization and angiogenesis of the endometrium during the menstrual cycle and decidualization.

Ultrasmall Superparamagnetic Iron Oxide Imaging Identifies Tissue and Nerve Inflammation in Pain Conditions.

Objective: Correlation between radiologic structural abnormalities and clinical symptoms in low back pain patients is poor. There is an unmet clinical need to image inflammation in pain conditions to aid diagnosis and guide treatment. Ferumoxytol, an ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle, is clinically used to treat iron deficiency anemia and showed promise in imaging tissue inflammation in human. We explored whether ferumoxytol can be used to identify tissue and nerve inflammation in pain conditions in animals and humans. Methods: Complete Freud's adjuvant (CFA) or saline was injected into mice hind paws to establish an inflammatory pain model. Ferumoxytol (20 mg/kg) was injected intravenously. Magnetic resonance imaging (MRI) was performed prior to injection and 72 hours postinjection. The changes in the transverse relaxation time (T2) before and after ferumoxytol injection were compared between mice that received CFA vs saline injection. In the human study, we administered ferumoxytol (4 mg/kg) to a human subject with clinical symptoms of lumbar radiculopathy and compared the patient with a healthy subject. Results: Mice that received CFA exhibited tissue inflammation and pain behaviors. The changes in T2 before and after ferumoxytol injection were significantly higher in mice that received CFA vs saline (20.8 ± 3.6 vs 2.2 ± 2.5, P = 0.005). In the human study, ferumoxytol-enhanced MRI identified the nerve root corresponding to the patient's symptoms, but the nerve root was not impinged by structural abnormalities, suggesting the potential superiority of this approach over conventional structural imaging techniques. Conclusions: Ferumoxytol-enhanced MRI can identify tissue and nerve inflammation and may provide a promising diagnostic tool in assessing pain conditions in humans.

Mitigation of reactive metabolite formation for a series of 3-amino-2-pyridone inhibitors of Bruton's tyrosine kinase (BTK).

Reactive metabolites have been putatively linked to many adverse drug reactions including idiosyncratic toxicities for a number of drugs with black box warnings or withdrawn from the market. Therefore, it is desirable to minimize the risk of reactive metabolite formation for lead molecules in optimization, in particular for non-life threatening chronic disease, to maximize benefit to risk ratio. This article describes our effort in addressing reactive metabolite issues for a series of 3-amino-2-pyridone inhibitors of BTK, e.g. compound 1 has a value of 459pmol/mg protein in the microsomal covalent binding assay. Parallel approaches were taken to successfully resolve the issues: establishment of a predictive screening assay with correlation association of covalent binding assay, identification of the origin of reactive metabolite formation using MS/MS analysis of HLM as well as isolation and characterization of GSH adducts. This ultimately led to the discovery of compound 7 (RN941) with significantly reduced covalent binding of 26pmol/mg protein.

Intravenous Ketamine Infusions for Neuropathic Pain Management: A Promising Therapy in Need of Optimization.

Intravenous ketamine infusions have been used extensively to treat often-intractable neuropathic pain conditions. Because there are many widely divergent ketamine infusion protocols described in the literature, the variation in these protocols presents a challenge for direct comparison of one protocol with another and in discerning an optimal protocol. Careful examination of the published literature suggests that ketamine infusions can be useful to treat neuropathic pain and that certain characteristics of ketamine infusions may be associated with better clinical outcomes. Increased duration of relief from neuropathic pain is associated with (1) higher total infused doses of ketamine; (2) prolonged infusion durations, although the rate of infusion does not appear to be a factor; and (3) coadministration of adjunct medications such as midazolam and/or clonidine that mitigate some of the unpleasant psychomimetic side effects. However, there are few studies designed to optimize ketamine infusion protocols by defining what an effective infusion protocol entails with regard to a respective neuropathic pain condition. Therefore, despite common clinical practice, the current state of the literature leaves the use of ketamine infusions without meaningful guidance from high-quality comparative evidence. The objectives of this topical review are to (1) analyze the available clinical evidence related to ketamine infusion protocols and (2) call for clinical studies to identify optimal ketamine infusion protocols tailored for individual neuropathic pain conditions. The Oxford Center for Evidence-Based Medicine classification for levels of evidence was used to stratify the grades of clinical recommendation for each infusion variable studied.

Nortriptyline Enhances Morphine-Conditioned Place Preference in Neuropathic Rats: Role of the Central Noradrenergic System.

BACKGROUND: Combination drug therapy is commonly used to treat chronic pain conditions such as neuropathic pain, and antidepressant is often used together with opioid analgesics. While rewarding is an intrinsic property of opioid analgesics, it is unknown whether the use of an antidepressant would influence opioid reward, which may contribute to opioid addiction. In this study, we examined whether nortriptyline (a tricyclic antidepressant and a first-line medication for neuropathic pain) would enhance the morphine rewarding property in both naive and chronic constriction sciatic nerve injury (CCI) rats. METHODS: The rewarding effect of these drugs was assessed using conditioned place preference (CPP). The real-time polymerase chain reaction, western blot, and enzyme-linked immunosorbent assay analysis were used to investigate the function of central noradrenergic system. RESULTS: In naive rats, coadministration of nortriptyline with morphine did not change the acquisition of morphine-induced CPP. However, nortriptyline enhanced the acquisition, delayed the extinction, and augmented the reinstatement of morphine-induced CPP in CCI rats. In CCI rats treated with both nortriptyline and morphine, the expression of α2A-adrenergic receptors, norepinephrine transporter, and tyrosine hydroxylase was markedly decreased in the locus coeruleus, whereas the norepinephrine concentration in the nucleus accumbens was remarkably increased. CONCLUSIONS: These results demonstrate that nortriptyline enhanced morphine reward when both drugs were used to treat neuropathic pain in rats and that this behavioral phenotype is likely to be mediated by upregulation of the central noradrenergic system. These findings may have implications in opioid therapy commonly used for chronic pain management.