RAF inhibitor LY3009120 sensitizes RAS or BRAF mutant cancer to CDK4/6 inhibition by abemaciclib via superior inhibition of phospho-RB and suppression of cyclin D1.

KRAS, NRAS and BRAF mutations are among the most important oncogenic drivers in many major cancer types, such as melanoma, lung, colorectal and pancreatic cancer. There is currently no effective therapy for the treatment of RAS mutant cancers. LY3009120, a pan-RAF and RAF dimer inhibitor advanced to clinical study has been shown to inhibit both RAS and BRAF mutant cell proliferation in vitro and xenograft tumor growth in vivo. Abemaciclib, a CDK4/6-selective inhibitor, is currently in phase III studies for ER-positive breast cancer and KRAS mutant lung cancer. In this study, we found that combinatory treatment with LY3009120 and abemaciclib synergistically inhibited proliferation of tumor cells in vitro and led to tumor growth regression in xenograft models with a KRAS, NRAS or BRAF mutation at the doses of two drugs that were well tolerated in combination. Further in vitro screen in 328 tumor cell lines revealed that tumor cells with KRAS, NRAS or BRAF mutation, or cyclin D activation are more sensitive, whereas tumor cells with PTEN, PIK3CA, PIK3R1 or retinoblastoma (Rb) mutation are more resistant to this combination treatment. Molecular analysis revealed that abemaciclib alone inhibited Rb phosphorylation partially and caused an increase of cyclin D1. The combinatory treatment cooperatively demonstrated more complete inhibition of Rb phosphorylation, and LY3009120 suppressed the cyclin D1 upregulation mediated by abemaciclib. These results were further verified by CDK4/6 siRNA knockdown. Importantly, the more complete phospho-Rb inhibition and cyclin D1 suppression by LY3009120 and abemaciclib combination led to more significant cell cycle G0/G1 arrest of tumor cells. These preclinical findings suggest that combined inhibition of RAF and d-cyclin-dependent kinases might provide an effective approach to treat patients with tumors harboring mutations in RAS or RAF genes.

A postpartum haemorrhage package with condom uterine balloon tamponade: a prospective multi-centre case series in Kenya, Sierra Leone, Senegal, and Nepal.

OBJECTIVE: To evaluate the effectiveness and safety of an ultra-low-cost uterine balloon tamponade package (ESM-UBT™) for facility-based management of uncontrolled postpartum haemorrhage (PPH) in Kenya, Sierra Leone, Senegal, and Nepal. DESIGN: Prospective multi-centre case series. SETTING: Facilities in resource-scarce areas of Kenya, Sierra Leone, Nepal, and Senegal. POPULATION: Women with uncontrolled postpartum haemorrhage in 307 facilities across the four countries. METHODS: A standardised ESM-UBT package was implemented in 307 facilities over 29 months (1 September 2012 to 1 February 2015). Data were collected via a multi-pronged approach including data card completion, chart reviews, and provider interviews. Beginning in August 2014, women who had previously undergone UBT placement were sought and queried regarding potential complications associated with UBT use. MAIN OUTCOME MEASURES: All-cause survival, survival from PPH, and post-UBT use complications (surgery, hospitalisation, antibiotics for pelvic infection) associated with UBT use. RESULTS: 201 UBTs were placed for uncontrolled vaginal haemorrhage refractory to all other interventions. In all, 38% (71/188) of women were either unconscious or confused at the time of UBT insertion. All-cause survival was 95% (190/201). However, 98% (160/163) of women survived uncontrolled PPH if delivery occurred at an ESM-UBT online facility. One (1/151) potential UBT-associated complication (postpartum endometritis) was identified and two improvised UBTs were placed in women with a ruptured uterus. CONCLUSIONS: These pilot data suggest that the ESM-UBT package is a clinically promising and safe method to arrest uncontrolled postpartum haemorrhage and save women's lives. The UBT was successfully placed by all levels of facility-based providers. Future studies are needed to further evaluate the effectiveness of ESM-UBT in low-resource settings. TWEETABLE ABSTRACT: Evidence for ESM-UBT as a clinically promising and safe method to arrest uncontrolled PPH and save women's lives.

Perinatal health care in a conflict-affected setting: evaluation of health-care services and newborn outcomes at a regional medical centre in Iraq.

A field-based assessment was conducted to assess maternal and newborn health-care services, perinatal and newborn outcomes and associated risk factors at Bint Al-Huda Maternal and Newborn Teaching Hospital, a large referral hospital in southern Iraq. The multi-method approach used interviews, discussions, observation and review of perinatal and newborn outcome data. There is limited assessment of maternal vital signs, labour pattern, fetal response, and complications during pregnancy and labour. Perinatal and neonatal mortality rates are 27.4/1000 births and 30.9/1000 live births respectively. Associated neonatal mortality factors were gestational age < 37 weeks, male sex, birth weight < 2.5 kg, maternal age > 35 years, rural maternal residence and vaginal delivery. Improving birth outcomes in southern Iraq requires evidence-based clinical guidelines, additional supplies and equipment, quality improvement initiatives and in-service training.

Perinatal health care in a conflict-affected setting: evaluation of health-care services and newborn outcomes at a regional medical centre in Iraq

A field-based assessment was conducted to assess maternal and newborn health-care services, perinatal and newborn outcomes and associated risk factors at Bint Al-Huda Maternal and Newborn Teaching Hospital, a large referral hospital in southern Iraq. The multi-method approach used interviews, discussions, observation and review of perinatal and newborn outcome data. There is limited assessment of maternal vital signs, labour pattern,fetal response, and complications during pregnancy and labour. Perinatal and neonatal mortality rates are 27.4/1000 births and 30.9/1000 live births respectively. Associated neonatal mortality factors were gestational age < 37 weeks, male sex,birth weight < 2.5 kg, maternal age > 35 years, rural maternal residence and vaginal delivery. Improving birth outcomes in southern Iraq requires evidence-based clinical guidelines, additional supplies and equipment, quality improvement initiatives and in-service training

Une évaluation sur le terrain a été menée afin d'analyser les services de soins de santé pour la mère et le nouveau-né, les issues périnatales et néonatales et les facteurs de risque associés au centre hospitalier universitaire pour la mère et l'enfant Bint Al-Huda, un grand hôpital de recours dans le sud de l'Iraq. L'approche reposait sur de multiples méthodes et a eu recours à des entretiens semi-structurés avec des informateurs clés, à des petits groupes de discussion, à l'observation de la pratique des soins et à l'examen des données concernant l'issue des soins périnatals et néonatals.Les signes vitaux chez la mère, le déroulement du travail, la réponse foetale et les complications pendant la grossesse et le travail sont peu évalués. Les taux de mortalité périnatale et néonatale sont de 27,4/1000 naissances et de 30,9/1000 naissances vivantes respectivement; les facteurs de mortalité néonatale associés étaient un âge gestationnel inférieur à 37 semaines,le sexe masculin, un poids de naissance inférieur à 2,5 kg, l'âge de la mère supérieur à 35 ans, un lieu de résidence rural, et un accouchement par voie basse. L'amélioration des issues néonatales dans le sud de l'Iraq passe par des recommandations cliniques fondées sur des bases factuelles,des fournitures et des équipements supplémentaires, des initiatives visant à améliorer la qualité et des formations en cours d'emploi

Development of a community-based maternal, newborn and child emergency training package in South Sudan.

OBJECTIVE: To develop an evidence-based maternal, newborn and child emergency training package for community-based frontline health workers (FHWs) in post-conflict South Sudan. METHODS: In partnership with the new Republic of South Sudan, a multimodal needs assessment was conducted through purposive sampling, involving key informant interviews, focus group discussions, provider knowledge assessments and facility surveys. Data were analyzed using traditional qualitative techniques and compared with existing training programmes and curricula. These findings informed the development and implementation of the novel training approach. RESULTS: The needs assessment involved 33 FHWs, eight diverse health facilities in Eastern Equatoria, and stakeholders within 18 governmental and non-governmental organizations. Significant consensus emerged regarding the need for greater capacity among previously untrained FHWs. A maternal, newborn and child health training package was developed that included: (1) a participatory training course taught through a 'training of trainers' approach; (2) nine different pictorial action-based checklists covering basic management and referral of maternal, newborn and child emergencies; and (3) essential setting-appropriate equipment. CONCLUSION: A novel maternal, newborn and child survival package was developed for previously untrained and illiterate FHWs in South Sudan. It is hoped that this approach will build community-based capacity in resource-limited settings while greater capacity is being developed for facility-based deliveries by skilled birth attendants.

Uterine balloon tamponade for the treatment of postpartum haemorrhage in resource-poor settings: a systematic review.

BACKGROUND: Effective interventions addressing postpartum haemorrhage (PPH) are critically needed to reduce maternal mortality worldwide. Uterine balloon tamponade (UBT) has been shown to be an effective technique to treat PPH in developed countries, but has not been examined in resource-poor settings. OBJECTIVES: This literature review examines the effectiveness of UBT for the treatment and management of PPH in resource-poor settings. SEARCH STRATEGY: Publications were sought through searches of five electronic databases: Medline, Cochrane Reference Libraries, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Embase and Popline. SELECTION CRITERIA: Titles and abstracts were screened for eligibility by two independent reviewers. Each reviewer evaluated the full text of potentially eligible articles by defined inclusion criteria, including the presentation of empirical data and use of UBT in resource-poor settings to treat PPH. DATA COLLECTION AND ANALYSIS: Full text of all eligible publications was collected and systematically coded. MAIN RESULTS: The search identified 13 studies that met the inclusion criteria: six case reports or case series, five prospective studies and two retrospective studies for a total of 241 women. No randomised controlled trials were identified. The studies used various types of UBT, including condom catheter (n = 193), Foley catheter (n = 5) and Sengstaken-Blakemore oesophageal tube (n = 1). In these studies, primarily conducted in tertiary-care settings rather than lower-level health facilities, UBT successfully treated PPH in 234 out of 241 women. CONCLUSIONS: UBT is an effective treatment for PPH in resource-poor settings. Further study of UBT interventions is necessary to better understand the barriers to successful implementation and use in these settings.

The market of human organs: a window into a poorly understood global business.

The global demand for human organs has set the stage for an exploding and poorly understood global business in human organs. Whenever there is demand for a product, the opportunity for business arises. The form that a business takes is dependent on a complex network of inputs and outputs, each affecting the others. Historically, the details of any specific market are drastically underestimated. Nowhere is this truer than in the market of human organs. The drivers, which propel the "goods" of human organs, form a flourishing business. Critical analysis is essential to understanding of the supply and demand sides and to determine the role of government in regulating the industry. Governmental groups have dismissed formation of a regulated market for organ sales. The concept is nonetheless a topic of active discussion, motivated by the suffering of patients in need of organs and exploitation of the victims of human trafficking. Ethical principles have been invoked on each side of the ensuing debate. Theory in the absence of sufficient data is shaky ground for enactment of new policy. The Aristotelian concept of "practical wisdom" and the pragmatism of William James illuminate the importance of scientific investigation as guide to policy formation. How will stakeholders benefit or lose? What impact might be anticipated in regard to organized medicine's social contract? What can we learn about cross-cultural differences and their effect on the global landscape?

Selective heterologous regulation of 5-HT1A receptor-stimulated 35S GTPgammaS binding in the anterior cingulate cortex as a result of 5-HT2 receptor activation.

Previous studies have shown that administration of the 5-HT(2) receptor agonist DOI to rats results in the heterologous desensitization of 5-HT(1A) receptor-mediated behavioral and neuroendocrine responses [Neuropsychopharmacology 19 (1998) 354; J. Neurosci. 21 (2001) 7919]. We hypothesized that the basis for these changes in 5-HT(1A) receptor function may involve changes in the capacity of the 5-HT(1A) receptor to activate G proteins. We examined the effect of chronic administration of DOI on the regulation of 5-HT(1A) receptor function at the level of receptor-G protein interaction using quantitative autoradiography of [(35)S]GTPgammaS binding stimulated by the 5-HT(1A) receptor agonist (+/-)8-OH-DPAT (1 microM). Repeated administration of DOI (1 mg/kg, s.c. once daily for 8 days) resulted in a marked down-regulation in 5-HT(2A) binding sites, as labeled by the antagonist radioligand [(3)H]ketanserin, throughout the cerebral cortex. Chronic DOI treatment also resulted in a significant and selective attenuation of 5-HT(1A) receptor-stimulated [(35)S]GTPgammaS binding in the anterior cingulate cortex (vehicle-treated: 74+/-7.7% above basal; DOI-treated: 43+/-4.6% above basal). Interestingly, 5-HT(1A) receptor-stimulated [(35)S]GTPgammaS binding was not altered in the dorsal or median raphe, or in the limbic structures and other cortical regions examined. The decrease in 5-HT(1A) receptor-stimulated [(35)S]GTPgammaS binding in anterior cingulate cortex was not due to a decrease in 5-HT(1A) receptor number, indicating that the capacity of the 5-HT(1A) receptor to activate G proteins is attenuated in this cortical area following repeated DOI treatment. The heterologous regulation of 5-HT(1A) receptor function by chronic 5-HT(2) receptor activation in the anterior cingulate cortex raises interesting questions as to how the regulatory interaction between these serotonin receptor subtypes influences cognition, memory and emotion.

Methocinnamox is a potent, long-lasting, and selective antagonist of morphine-mediated antinociception in the mouse: comparison with clocinnamox, beta-funaltrexamine, and beta-chlornaltrexamine.

The irreversible mu-opioid antagonists beta-funaltrexamine (beta-FNA) and beta-chlornaltrexamine (beta-CNA) are important pharmacological tools but have a kappa-agonist activity and, in the latter case, low selectivity. This work examines whether clocinnamox (C-CAM) and the newer analog, methocinnamox (M-CAM), represent improved long-lasting antagonists for examining mu-opioid-mediated effects in vivo. beta-FNA, beta-CNA, C-CAM, and M-CAM were compared after systemic administration in mice and in vitro. beta-FNA and beta-CNA were effective agonists in the writhing assay, reversible by the kappa-antagonist norbinaltorphimine. Neither C-CAM nor M-CAM had agonist activity in vivo. M-CAM was devoid of agonist action at cloned opioid receptors. All four compounds depressed the dose-effect curve for the mu-agonist morphine in the warm-water tail-withdrawal test 1 h after administration; at 48 h, recovery was evident. In the writhing assay, the dose-effect curve for morphine was shifted in a parallel fashion in the order M-CAM >> C-CAM > beta-CNA > or = beta-FNA. In comparison with their ability to shift the dose-effect curve for bremazocine (kappa) and BW373U86 (delta), beta-CNA was the least mu-selective, followed by C-CAM < beta-FNA < M-CAM. M-CAM (1.8 mg/kg) produced a 74-fold increase in the ED(50) of morphine while showing no effect on bremazocine or BW373U86 dose-response curves. In binding assays, C-CAM and M-CAM were 8-fold selective for mu- over kappa-receptors, whereas beta-FNA and beta-CNA were mu/delta-, but not mu/kappa, selective. However, ex vivo binding assays confirmed the mu-receptor selectivity of M-CAM. M-CAM is thus a potent, long-lasting, and specific antagonist at mu-receptors in vivo that lacks confounding agonist actions.

Characterization of P5, a novel NFAT/AP-1 site in the human IL-4 promoter.

Interleukin 4 (IL-4) gene expression is controlled at the level of transcription by the complex interactions of multiple factors that bind to a proximal promoter region. Nuclear factor of activated T cells (NFAT) can bind up to five purine-rich sequences in the IL-4 promoter termed the P elements (P0-P4). In this paper, we characterize a novel P element in the upstream region of the human IL-4 promoter that we term P5. P5 shares a core NFAT motif ((-353)GGAAA(-357)) and additional sequence similarity with the other P elements and supported strong interactions between the NFATp DNA-binding domain (DBD) and the AP-1 proteins cFos and cJun in DNA-binding assays. Inducibility of the IL-4 promoter was significantly impaired in a reporter construct in which the P5 element was mutated in the context of the full-length promoter. We conclude that P5 represents a novel IL-4 promoter P element that contributes to IL-4 promoter inducibility.

Glucocorticoids inhibit calcium- and calcineurin-dependent activation of the human IL-4 promoter.

The mechanism by which glucocorticoids (GC) inhibit IL-4 gene expression is currently unknown. In T lymphocytes, IL-4 gene expression is regulated at the level of transcription by increases in intracellular calcium concentration and by the calcium-activated phosphatase calcineurin. In this paper we report that dexamethasone (Dex) inhibits calcium ionophore-induced activation of the human IL-4 promoter in transiently transfected Jurkat T cells. Inhibition of the promoter by Dex is dependent on expression of the GC receptor (GR), because it does not occur in GR-deficient cells. Dex also represses activation of the promoter induced by cotransfecting cells with a constitutively active mutant of calcineurin. Using a series of deletion constructs, we show that the proximal 95 bp of the IL-4 promoter contain a Dex-sensitive regulatory element. This region contains the P1 sequence, a proximal binding site for NF-AT. A calcium-induced but Dex-inhibited nuclear complex containing NF-AT binds to the P1 element in EMSA. Using immunoprecipitation under nondenaturing conditions, we found that the GRalpha isoform coprecipitates with NF-ATc in nuclear extracts of calcium ionophore- and Dex-treated cells. Taken together, our results show that GC inhibit IL-4 gene expression by interfering with NF-AT-dependent transactivation of the proximal human IL-4 promoter.

Rapid reversal of life-threatening diltiazem-induced tetany with calcium chloride.

We describe a patient who developed tetany with sudden respiratory arrest after the infusion of intravenous diltiazem. The administration of calcium chloride rapidly resolved the patient's tetany with prompt recovery of respiratory function, averting the need for more aggressive airway management and ventilatory support. The emergency physician should be aware that life-threatening tetany may accompany the administration of intravenous diltiazem and that calcium chloride may be a rapid and effective remedy.

Stat6 inhibits human interleukin-4 promoter activity in T cells.

The differentiation of naive T-helper (Th) cells into cytokine-secreting effector Th cells requires exposure to multiple signals, including exogenous cytokines. Interleukin-4 (IL-4) plays a major role in this process by promoting the differentiation of IL-4-secreting Th2 cells. In Th2 cells, IL-4 gene expression is tightly controlled at the level of transcription by the coordinated binding of multiple transcription factors to regulatory elements in the proximal promoter region. Nuclear factor of activated T cell (NFAT) family members play a critical role in regulating IL-4 transcription and interact with up to five sequences (termed P0 through P4) in the IL-4 promoter. The molecular mechanisms by which IL-4 induces expression of the IL-4 gene are not known, although the IL-4-activated transcription factor signal transducer and activator of transcription 6 (Stat6) is required for this effect. We report here that Stat6 interacts with three binding sites in the human IL-4 promoter by electrophoretic mobility shift assays. These sites overlap the P1, P2, and P4 NFAT elements. To investigate the role of Stat6 in regulating IL-4 transcription, we used Stat6-deficient Jurkat T cells with different intact IL-4 promoter constructs in cotransfection assays. We show that, whereas a multimerized response element from the germline IgE promoter was highly induced by IL-4 in Stat6-expressing Jurkat cells, the intact human IL-4 promoter was repressed under similar conditions. We conclude that the function of Stat6 is highly dependent on promoter context and that this factor promotes IL-4 gene expression in an indirect manner.

Large-diameter suction tubing significantly improves evacuation time of simulated vomitus.

Current suction equipment is often inadequate at clearing the oropharynx. This study tested the hypothesis that evacuation times of simulated vomitus could be significantly improved by increasing suction tube and connection port diameters. Two standard suction systems and a new large-diameter suction system were tested. Mean evacuation times for 90 mL (an average mouthful) of three different vomitus-simulating substances--water, activated charcoal, and Progresso vegetable soup--were compared. All parameters other than suction tubing and attachment port diameters remained constant. The data were analyzed with analysis of variance and Fisher's protected least significant difference post hoc test. Use of large-diameter suction tubing significantly (P < .0001) improved evacuation time for each of the three substances. This improvement was most evident in the trials with activated charcoal and the vegetable soup, where there was a tenfold decrease in mean evacuation time. These results show that large-diameter 3/4-inch suction tubing connected to the 1-inch port is superior to the standard 1/4-inch tubing and connection ports currently used. The tenfold reduction in evacuation time of viscous and particulate materials may have important clinical implications in preventing or minimizing complications from aspiration.

Identification of a BRCA1-associated kinase with potential biological relevance.

A biochemical approach was used to identify proteins which interact with human BRCA1. Through this work, a kinase activity which co-purifies with BRCA1 has been identified. This kinase activity, which phosphorylates BRCA1 in vitro, was originally identified in Sf9 insect cells but is also present in cells of human origin including breast and ovarian carcinoma cell lines. The BRCA1 kinase activity in vitro is associated with a fragment of BRCA1 encompassing amino acids 329-435. This peptide is also phosphorylated in various human cell lines. A computer-assisted sequence analysis revealed that this peptide was a potential substrate for phosphorylation by PKA, PKC, or CKII. However, phosphorylation by these kinases could not be demonstrated in vitro indicating the presence of another kinase activity. Phosphorylation in vitro requires a minimal domain of BRCA1 encompassing amino acids 379-408. Notably, deletion of this minimal domain abolishes growth suppression by BRCA1 indicating that this domain, as well as phosphorylation within this domain, may be important for BRCA1 function.

Butorphanol-mediated antinociception in mice: partial agonist effects and mu receptor involvement.

In the present experiments, we characterized the agonist and antagonist effects of butorphanol in mice. In the mouse radiant-heat tail-flick test, the mu agonists morphine and fentanyl and the kappa agonist U50,488H were fully effective as analgesics, whereas butorphanol was partially effective (producing 82% of maximal possible analgesic effect). Naltrexone was approximately equipotent in antagonizing the effects of morphine, fentanyl and butorphanol; in vivo apparent pA2 values for these naltrexone/agonist interactions were 7.5 (unconstrained). Naltrexone was approximately 10 times less potent in antagonizing the effect of U50,488H (average apparent pK(B) = 6.7). The selective mu antagonist beta-funaltrexamine (0.1-1.0 mg/kg) antagonized the effects of butorphanol in a dose-dependent insurmountable manner. Pretreatment with nor-binaltorphimine (32 mg/kg), a kappa-selective antagonist, did not reliably antagonize butorphanol, and naltrindole (20 and 32 mg/kg), a delta-selective antagonist, failed to antagonize the effects of butorphanol. Low doses of butorphanol (1.0, 1.8 or 3.2 mg/kg) caused parallel, rightward shifts in the dose-effect curve for morphine and parallel leftward shifts in the dose-effect curve for U50,488H. Taken together, the results of the present study suggest that butorphanol is a partial agonist in the mouse radiant-heat tail-flick test and that activity at mu receptors accounts for the majority of its antinociceptive effects.

Intravenous morphine for early pain relief in patients with acute abdominal pain.

OBJECTIVE: To determine whether morphine affects evaluation or outcome for patients with acute abdominal pain. METHODS: Prospective, double-blind, placebo-controlled administration of morphine sulfate (MS) or normal saline (NS) in the setting of acute abdominal pain. The study was performed at a military ED with an annual census of 60,000 visits. Patients > or = 18 years old who had abdominal pain for < or = 48 hours were included. Patients who were allergic to MS or who had systolic blood pressures < 90 mm Hg were excluded. The physicians indicated a provisional diagnosis, a differential diagnosis, and a provisional disposition. Study solution was titrated to the patient's assessment of adequate analgesia (up to a volume equivalent of 20 mg of MS); pain response was monitored using a visual analog scale (VAS). The patients were followed until diagnosis occurred or symptoms resolved. RESULTS: Of 75 patients enrolled, 71 completed the study; 35 patients received MS and 36 received NS. More than half (44; 62%) of the patients were admitted from the ED; 28 patients underwent surgery. The VAS pain level improved more for the MS group, 3.9 +/- 2.8 cm, than it did for the NS group, 0.8 +/- 1.5 cm (p < 0.01). Study solution dose was less in the MS group than it was in the NS group, 1.5 +/- 0.5 mL vs 1.8 +/- 0.4 mL (p < 0.01). There was no difference between the groups when comparing accuracy of provisional or differential diagnosis with that of final diagnosis. Differences between provisional and actual dispositions were the same in all groups. There were 3 diagnostic or management errors in each group. CONCLUSIONS: When compared with saline placebo, the administration of MS to patients with acute abdominal pain effectively relieved pain and did not alter the ability of physicians to accurately evaluate and treat patients.

[3H]MK-801 binding to well-washed rat brain membranes following cessation of chronic phencyclidine treatment.

Rats were implanted with osmotic minipumps SC that infused either saline or 10 mg/kg/day phencyclidine (PCP) for 10 days, a regimen that produces dependence to PCP. At the end of this 10-day infusion period, the pumps were removed and the rats were sacrificed either immediately or at various time points (12 h, 1, 2, and 7 days) after pump removal. The saturation binding parameters of [3H]MK-801 were then determined in well-washed cortical/hippocampal membranes prepared from these rats. Neither the Bmax nor the Kd of [3H]MK-801 binding in membranes of PCP-treated rats differed from that determined using membranes from saline-treated rats at any time point studied. These results suggest that alterations in PCP receptors do not play a major role in the production of PCP dependence.

Receptor reserve and affinity of mu opioid agonists in mouse antinociception: correlation with receptor binding.

In order to quantitate the extent to which opioid agonist potencies obtained in behavioral assays are determined by the apparent in vivo affinity and efficacy of the agonist, the antinociceptive effects of the mu opioid agonists morphine, fentanyl, etonitazene, and NIH 10741 were assessed before and after administration of the insurmountable mu opioid antagonist clocinnamox (CCAM) in a 55 degrees C warm-water tail withdrawal test in Swiss albino mice. Under control conditions, all four mu opioid agonists produced a full antinociceptive response with the following ED50 values (in mg/kg): morphine, 12; fentanyl, 0.47; etonitazene, 0.039; NIH 10741, 0.0051. Analysis of CCAM's effects according to Black and Leff gave the following agonist efficacy or tau values: Morphine, 4; fentanyl 15, etonitazene, 7; and NIH 10741, 59. The respective KA values were (in mg/kg): morphine, 29; fentanyl, 7.3; etonitazene, 0.22; and NIH 10741, 0.30. The major determinant of the experimentally observed ED50 values seemed to be the apparent in vivo affinity of the respective agonist and not its efficacy. KA values (expressed as mol/kg) correlated with the Ki values (in mol/l) obtained with [3H]DAMGO radioligand binding (r = 0.96 for pKA vs. pKi), although being on average 11,000-fold higher. Values for q, the available receptor fraction as determined in the behavioral experiments, correlated strongly (r = 0.96) with the q values determined by ex vivo [3H]DAMGO- and [3H]naltrexone equilibrium binding (i.e., Bmax,clocinnamox/Bmax,control), the relationship approaching unity.