Kimberly Vellano

A subunit-selective potentiator of NR2C- and NR2D-containing NMDA receptors

NMDA receptors are tetrameric complexes of NR1 and NR2A-D subunits that mediate excitatory synaptic transmission and have a role in neurological disorders. In this article, we identify a novel subunit-selective potentiator of NMDA receptors containing the NR2C or NR2D subunit, which could allow selective modification of circuit function in regions expressing NR2C/D subunits. The substituted tetrahydroisoquinoline CIQ (3-chlorophenyl)(6,7-dimethoxy-1-((4-methoxyphenoxy)methyl)-3,4-dihydroisoquinolin-2(1H)-yl)methanone) enhances receptor responses two-fold with an EC(50) of 3 μM by increasing channel opening frequency without altering mean open time or EC(50) values for glutamate or glycine. The actions of CIQ depend on a single residue in the M1 region (NR2D Thr592) and on the linker between the N-terminal domain and agonist binding domain. CIQ potentiates native NR2D-containing NMDA receptor currents from subthalamic neurons. Our identification of a subunit-selective NMDA receptor modulator reveals a new class of pharmacological tools with which to probe the role of NR2C- and NR2D-containing NMDA receptors in brain function and disease.

Structural Determinants of D-Cycloserine Efficacy at the NR1/NR2C NMDA Receptors

We have studied relative efficacies of NR1 agonists glycine and d-cycloserine (DCS), and found efficacy to be dependent on the NR2 subunit. DCS shows partial agonism at NR1/NR2B but has higher relative efficacy than glycine at NR1/NR2C receptor. Molecular dynamics (MD) simulations of the NR1/NR2B and NR1/NR2C agonist binding domain dimer suggest only subtle differences in the interactions of DCS with NR1 binding site residues relative to glycine. The most pronounced differences were observed in the NR1/NR2C simulation between the orientation of helices F and G of the NR1 subunit. Interestingly, Helix F was previously proposed to influence receptor gating and to adopt an orientation depending on agonist efficacy. MD simulations and site-directed mutagenesis further suggest a role for residues at the agonist binding domain dimer interface in regulating DCS efficacy. To relate the structural rearrangements to receptor gating, we recorded single-channel currents from outside-out patches containing a single active NR1/NR2C receptor. DCS increased the mean open time and open probability of NR1/NR2C receptors compared with glycine. Maximum likelihood fitting of a gating model for NR1/NR2C receptor activation to the single-channel data suggests that DCS specifically accelerates the rate constant governing a fast gating step and reduces the closing rate. These changes appear to reflect a decreased activation energy for a pregating step and increased stability of the open states. We suggest that the higher efficacy of DCS at NR1/NR2C receptors involves structural rearrangements at the dimer interface and an effect on NR1/NR2C receptor pregating conformational changes.

Quinazolin-4-one derivatives: A novel class of non-competitive NR2C/D subunit-selective N-methyl-D-aspartate receptor antagonists

We describe a new class of subunit-selective antagonists of N-methyl D-aspartate (NMDA)-selective ionotropic glutamate receptors that contain the (E)-3-phenyl-2-styrylquinazolin-4(3H)-one backbone. The inhibition of recombinant NMDA receptor function induced by these quinazolin-4-one derivatives is noncompetitive and voltage-independent, suggesting that this family of compounds does not exert action on the agonist binding site of the receptor or block the channel pore. The compounds described here resemble CP-465,022 ((S)-3-(2-chlorophenyl)-2-[2-(6-diethylaminomethyl-pyridin-2-yl)-vinyl]-6-fluoro-3H-quinazolin-4-one), a noncompetitive antagonist of AMPA-selective glutamate receptors. However, modification of ring substituents resulted in analogues with greater than 100-fold selectivity for recombinant NMDA receptors over AMPA and kainate receptors. Furthermore, within this series of compounds, analogues were identified with 50-fold selectivity for recombinant NR2C/D-containing receptors over NR2A/B containing receptors. These compounds represent a new class of noncompetitive subunit-selective NMDA receptor antagonists.

Regional Variation in Out-of-Hospital Cardiac Arrest Survival in the United States

Background— Although previous studies have shown marked variation in out-of-hospital cardiac arrest survival across US regions, factors underlying this survival variation remain incompletely explained. Methods and Results— Using data from the Cardiac Arrest Registry to Enhance Survival, we identified 96 662 adult patients with out-of-hospital cardiac arrest in 132 US counties. We used hierarchical regression models to examine county-level variation in rates of survival and survival with functional recovery (defined as Cerebral Performance Category score of 1 or 2) and examined the contribution of demographics, cardiac arrest characteristics, bystander cardiopulmonary resuscitation, automated external defibrillator use, and county-level sociodemographic factors in survival variation across counties. A total of 9317 (9.6%) patients survived to discharge, and 7176 (7.4%) achieved functional recovery. At a county level, there was marked variation in rates of survival to discharge (range, 3.4%–22.0%; median odds ratio, 1.40; 95% confidence interval, 1.32–1.46) and survival with functional recovery (range, 0.8%–21.0%; median odds ratio, 1.53; 95% confidence interval, 1.43–1.62). County-level rates of bystander cardiopulmonary resuscitation and automated external defibrillator use were positively correlated with both outcomes (P<0.0001 for all). Patient demographic and cardiac arrest characteristics explained 4.8% and 27.7% of the county-level variation in survival, respectively. Additional adjustment of bystander cardiopulmonary resuscitation and automated external defibrillator explained 41% of the survival variation, and this increased to 50.4% after adjustment of county-level sociodemographic factors. Similar findings were noted in analyses of survival with functional recovery. Conclusions— Although out-of-hospital cardiac arrest survival varies significantly across US counties, a substantial proportion of the variation is attributable to differences in bystander response across communities.

Implementation of a Fluorescence-Based Screening Assay Identifies Histamine H3 Receptor Antagonists Clobenpropit and Iodophenpropit as Subunit-Selective N-Methyl-d-Aspartate Receptor Antagonists

N-Methyl-d-aspartate (NMDA) receptors are ligand-gated ion channels that mediate a slow, Ca2+-permeable component of excitatory synaptic transmission in the central nervous system and play a pivotal role in synaptic plasticity, neuronal development, and several neurological diseases. We describe a fluorescence-based assay that measures NMDA receptor-mediated changes in intracellular calcium in a BHK-21 cell line stably expressing NMDA receptor NR2D with NR1 under the control of a tetracycline-inducible promoter (Tet-On). The assay selectively identifies allosteric modulators by using supramaximal concentrations of glutamate and glycine to minimize detection of competitive antagonists. The assay is validated by successfully identifying known noncompetitive, but not competitive NMDA receptor antagonists among 1800 screened compounds from two small focused libraries, including the commercially available library of pharmacologically active compounds. Hits from the primary screen are validated through a secondary screen that used two-electrode voltage-clamp recordings on recombinant NMDA receptors expressed in Xenopus laevis oocytes. This strategy identified several novel modulators of NMDA receptor function, including the histamine H3 receptor antagonists clobenpropit and iodophenpropit, as well as the vanilloid receptor transient receptor potential cation channel, subfamily V, member 1 (TRPV1) antagonist capsazepine. These compounds are noncompetitive antagonists and the histamine H3 receptor ligand showed submicromolar potency at NR1/NR2B NMDA receptors, which raises the possibility that compounds can be developed that act with high potency on both glutamate and histamine receptor systems simultaneously. Furthermore, it is possible that some actions attributed to histamine H3 receptor inhibition in vivo may also involve NMDA receptor antagonism.

Association of Bystander Cardiopulmonary Resuscitation With Overall and Neurologically Favorable Survival After Pediatric Out-of-Hospital Cardiac Arrest in the United States: A Report From the Cardiac Arrest Registry to Enhance Survival Surveillance Registry

Importance There are few data on the prevalence or outcome of bystander cardiopulmonary resuscitation (BCPR) in children 18 years and younger. Objective To characterize BCPR in pediatric out-of-hospital cardiac arrests (OHCAs). Design, Setting, and Participants This analysis of the Cardiac Arrest Registry to Enhance Survival database investigated nontraumatic OHCAs in children 18 years and younger from January 2013 through December 2015. Exposures Bystander CPR, which included conventional CPR and compression-only CPR. Main Outcomes and Measures Overall survival and neurologically favorable survival, defined as a Cerebral Performance Category score of 1 or 2, at the time of hospital discharge. Results Of the 3900 children younger than 18 years with OHCA, 2317 (59.4%) were infants, 2346 (60.2%) were female, and 3595 (92.2%) had nonshockable rhythms. Bystander CPR was performed on 1814 children (46.5%) and was more common for white children (687 of 1221 [56.3%]) compared with African American children (447 of 1134 [39.4%]) and Hispanic children (197 of 455 [43.3%]) (P < .001). Overall survival and neurologically favorable survival were 11.3% (440 of 3900) and 9.1% (354 of 3900), respectively. On multivariable analysis, BCPR was independently associated with improved overall survival (adjusted proportion, 13.2%; 95% CI, 11.81-14.58; adjusted odds ratio, 1.57; 95% CI, 1.25-1.96) and neurologically favorable survival (adjusted proportion, 10.3%; 95% CI, 9.10-11.54; adjusted odds ratio, 1.50; 95% CI, 1.21-1.98) compared with no BCPR (overall survival: adjusted proportion, 9.5%; 95% CI, 8.28-10.69; neurologically favorable survival: adjusted proportion, 7.59%; 95% CI, 6.50-8.68). For those with data on type of BCPR, 697 of 1411 (49.4%) received conventional CPR and 714 of 1411 (50.6%) received compression-only CPR. On multivariable analysis, only conventional CPR (adjusted proportion, 12.89%; 95% CI, 10.69-15.09; adjusted odds ratio, 2.06; 95% CI, 1.51-2.79) was associated with improved neurologically favorable survival compared with no BCPR (adjusted proportion, 9.59%; 95% CI, 6.45-8.61). There was a significant interaction of BCPR with age. Among infants, conventional BCPR was associated with improved overall survival and neurologically favorable survival while compression-only CPR had similar outcomes to no BCPR. Conclusions and Relevance Bystander CPR is associated with improved outcomes in pediatric OHCAs. Improving the provision of BCPR in minority communities and increasing the use of conventional BCPR may improve outcomes for children with OHCA.

Evaluating Dispatch-Assisted CPR Using the CARES Registry

Abstract Objectives: Dispatch-assisted cardiopulmonary resuscitation (DA-CPR) has been shown to improve cardiac arrest survival. Recent literature has proposed dispatch metrics for provision of this intervention. Our objectives are to: use the Cardiac Arrest Registry to Enhance Survival (CARES) to compare current practice to proposed DA-CPR guidelines; describe barriers to DA-CPR; and assess the association of DA-CPR with out-of-hospital cardiac arrest (OHCA) survival. Methods: We reviewed data from structured dispatch reviews of 911 OHCA calls from 1/1/14–12/31/15. Dispatch data including whether dispatch CPR instruction was given, and time intervals to CPR instruction and provision were linked with OHCA data elements from field cardiac arrest process and outcome data. Descriptive data on barriers to dispatch-caller instruction and measures of dispatcher performance were calculated. We compared outcome of patients who received bystander CPR prior to the 911 call (BCPR), after dispatcher CPR instructions (DA-CPR), and not until Emergency Medical Services (EMS) arrival (no BCPR). Results: We identified 3335 cases from 32 dispatch agencies in 9 states that had dispatch and outcome data. CPR was performed prior to the 911 call by a bystander in 496 (14.9%) cases. Of all calls where the dispatcher talked to a bystander, dispatchers recognized cardiac arrest in 82.9% cases (1514/1827), with 31.6% calls recognized in <60 seconds. DA-CPR instructions were initiated in most (1320/1514, 87.2%) cases, and cardiac compressions were initiated in 73.7% (973/1320). DA-CPR was performed < two minutes in 21.4% of cases. In a multivariable analysis, BCPR (CPR prior to EMS arrival without instructions given) was associated with significantly improved patient survival (OR = 1.49, 95% CI 1.09, 2.04), and DA-CPR a non-significant improvement in survival to discharge (OR = 1.19, 95% CI 0.91, 1.56). Conclusions: Temporal measures of dispatch performance were substantially below proposed national standards. In this population, OHCA was frequently recognized and DA-CPR performed but was not associated with a significant improvement in survival.

Out-of-hospital cardiac arrest survival in international airports

BACKGROUND The highest achievable survival rate following out-of-hospital cardiac arrest is unknown. Data from airports serving international destinations (international airports) provide the opportunity to evaluate the success of pre-hospital resuscitation in a relatively controlled but real-life environment. METHODS This retrospective cohort study included all cases of out-of-hospital cardiac arrest at international airports with resuscitation attempted between January 1st, 2013 and December 31st, 2015. Crude incidence, patient, event characteristics and survival to hospital discharge/survival to 30 days (survival) were calculated. Mixed effect logistic regression analyses were performed to identify predictors of survival. Variability in survival between airports/countries was quantified using the median odds ratio. RESULTS There were 800 cases identified, with an average of 40 per airport. Incidence was 0.024/100,000 passengers per year. Percentage survival for all patients was 32%, and 58% for patients with an initial shockable heart rhythm. In adjusted analyses, initial shockable heart rhythm was the strongest predictor of survival (odds ratio, 36.7; 95% confidence interval [CI], 15.5-87.0). In the bystander-witnessed subgroup, delivery of a defibrillation shock by a bystander was a strong predictor of survival (odds ratio 4.8; 95% CI, 3.0-7.8). Grouping of cases was significant at country level and survival varied between countries. CONCLUSIONS In international airports, 32% of patients survived an out-of-hospital cardiac arrest, substantially more than in the general population. Our analysis suggested similarity between airports within countries, but differences between countries. Systematic data collection and reporting are essential to ensure international airports continually maximise activities to increase survival.

Neighborhood characteristics, bystander automated external defibrillator use, and patient outcomes in public out-of-hospital cardiac arrest

BACKGROUND Automated external defibrillators (AEDs) can be used by bystanders to provide rapid defibrillation for patients with out-of-hospital cardiac arrest (OHCA). Whether neighborhood characteristics are associated with AED use is unknown. Furthermore, the association between AED use and outcomes has not been well characterized for all (i.e. shockable and non-shockable) public OHCAs. METHODS We included public, non-911-responder witnessed OHCAs registered in the Cardiac Arrest Registry to Enhance Survival (CARES) between 2013 and 2016. The primary patient outcome was survival to hospital discharge with a favorable functional outcome. We first assessed the association between neighborhood characteristics and bystander AED use using logistic regression and then assessed the association between bystander AED use and patient outcomes in a propensity score matched cohort. RESULTS 25,182 OHCAs were included. Several neighborhood characteristics, including the proportion of people living alone, the proportion of white people, and the proportion with a high-school degree or higher, were associated with bystander AED use. 5132 OHCAs were included in the propensity score-matched cohort. Bystander AED use was associated with an increased risk of a favorable functional outcome (35% vs. 25%, risk difference: 9.7% [95% confidence interval: 7.2%, 12.2%], risk ratio: 1.38 [95% confidence interval: 1.27, 1.50]). This was driven by increased favorable functional outcomes with AED use in patients with shockable rhythms (58% vs. 39%) but not in patients with non-shockable rhythms (10% vs. 10%). CONCLUSIONS Specific neighborhood characteristics were associated with bystander AED use in OHCA. Bystander AED use was associated with an increase in favorable functional outcome.

Automated External Defibrillator Application Before EMS Arrival in Pediatric Cardiac Arrests

Using pediatric data from CARES, we examine in this article patient- and neighborhood-level characteristics associated with pre-EMS AED application. BACKGROUND: Little is known about the predictors of pre–emergency medical service (EMS) automated external defibrillator (AED) application in pediatric out-of-hospital cardiac arrests. We sought to determine patient- and neighborhood-level characteristics associated with pre-EMS AED application in the pediatric population. METHODS: We reviewed prospectively collected data from the Cardiac Arrest Registry to Enhance Survival on pediatric patients (age >1 to ≤18 years old) who had out-of-hospital nontraumatic arrest (2013–2015). RESULTS: A total of 1398 patients were included in this analysis (64% boys, 45% white, and median age of 11 years old). An AED was applied in 28% of the cases. Factors associated with pre-EMS AED application in univariable analyses were older age (odds ratio [OR]: 1.9; 12–18 years old vs 2–11 years old; P < .001), white versus African American race (OR: 1.4; P = .04), public location (OR: 1.9; P < .001), witnessed status (OR: 1.6; P < .001), arrests presumed to be cardiac versus respiratory etiology (OR: 1.5; P = .02) or drowning etiology (OR: 2.0; P < .001), white-populated neighborhoods (OR: 1.2 per 20% increase in white race; P = .01), neighborhood median household income (OR: 1.1 per