ß-Blocker Use and Risk of Mortality in Heart Failure Patients Initiating Maintenance Dialysis.

RATIONAL & OBJECTIVE: Beta-blockers are recommended for patients with heart failure (HF) but their benefit in the dialysis population is uncertain. Beta-blockers are heterogeneous, including with respect to their removal by hemodialysis. We sought to evaluate whether ß-blocker use and their dialyzability characteristics were associated with early mortality among patients with chronic kidney disease with HF who transitioned to dialysis. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Adults patients with chronic kidney disease (aged≥18 years) and HF who initiated either hemodialysis or peritoneal dialysis during January 1, 2007, to June 30, 2016, within an integrated health system were included. EXPOSURES: Patients were considered treated with ß-blockers if they had a quantity of drug dispensed covering the dialysis transition date. OUTCOMES: All-cause mortality within 6 months and 1 year or hospitalization within 6 months after transition to maintenance dialysis. ANALYTICAL APPROACH: Inverse probability of treatment weights using propensity scores was used to balance covariates between treatment groups. Cox proportional hazard analysis and logistic regression were used to investigate the association between ß-blocker use and study outcomes. RESULTS: 3,503 patients were included in the study. There were 2,115 (60.4%) patients using ß-blockers at transition. Compared with nonusers, the HR for all-cause mortality within 6 months was 0.79 (95% CI, 0.65-0.94) among users of any ß-blocker and 0.68 (95% CI, 0.53-0.88) among users of metoprolol at transition. There were no observed differences in all-cause or cardiovascular-related hospitalization. LIMITATIONS: The observational nature of our study could not fully account for residual confounding. CONCLUSIONS: Beta-blockers were associated with a lower rate of mortality among incident hemodialysis patients with HF. Similar associations were not observed for hospitalizations within the first 6 months following transition to dialysis.

Investigational anabolic therapies for osteoporosis.

IMPORTANCE OF THE FIELD: Anabolic therapy, or stimulating the function of bone-forming osteoblasts, is the preferred pharmacological intervention for osteoporosis. AREAS COVERED IN THIS REVIEW: We reviewed bone anabolic agents currently under active investigation. The bone anabolic potential of IGF-I and parathyroid hormone-related protein is discussed in the light of animal data and human studies. We also discuss the use of antagonists of the calcium-sensing receptor (calcilytics) as orally administered small molecules capable of transiently elevating serum parathyroid hormone (PTH). Further, we reviewed novel anabolic agents targeting members of the wingless tail (Wnt) signaling family that regulate bone formation including DKK-1, sclerostin, Thp1, and glycogen synthase kinase 3beta. We have also followed up on the promise shown by beta-blockers in modulating the activity of sympathetic nervous system, thus affecting bone anabolism. We give critical consideration to neutralizing the activity of activin A, a negative regulator of bone mass by soluble activin receptor IIA, as a strategy to promote bone formation. WHAT THE READER WILL GAIN: Update on various strategies to promote osteoblast function currently under evaluation. TAKE HOME MESSAGE: In spite of favorable results in experimental models, none of these strategies has yet achieved the ultimate goal of providing an alternative to injectable PTH, the sole anabolic therapy in clinical use.

Central leptin action improves skeletal muscle AKT, AMPK, and PGC1 alpha activation by hypothalamic PI3K-dependent mechanism.

Central leptin action requires PI3K activity to modulate glucose homeostasis and peripheral metabolism. However, the mechanism behind this phenomenon is not clearly understood. We hypothesize that hypothalamic PI3K activity is important for the modulation of the AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) pathway, PGC1 alpha, and AKT in skeletal muscle (SM). To address this issue, we injected leptin into the lateral ventricle of rats. Hypothalamic JAK2 and AKT were activated by intracerebroventricular (ICV) injection of leptin in a time-dependent manner. Central leptin improved tolerance to glucose (GTT), increased PGC1 alpha expression, and AKT, AMPK, ACC and JAK2 phosphorylation in the soleus muscle. Previous ICV administration of either LY294002 or propranolol (IP) blocked these effects. We concluded that the activation of the hypothalamic PI3K pathway is important for leptin-induced AKT phosphorylation, as well as for active catabolic pathway through AMPK and PGC1 alpha in SM. Thus, a defective leptin signalling PI3K pathway in the hypothalamus may contribute to peripheral resistance to insulin associated to diet-induced obesity.

The use and value of in vitro technologies in metabolism studies.

The detailed investigation of the metabolism of drugs is one of the key issues in drug development. Several in vitro metabolism assays have been developed over the last two decades, to replace time-consuming and expensive animal studies. These have the potential to speed up drug development and increase drug safety, as they can be used to improve the prediction of the effects of drugs on humans. The key factors to be identified in metabolism are: a) the enzymes involved, and b) the metabolites produced by these enzymes. Cytochromes P450 (CYP-450s) are the key enzymes in drug metabolism. Cloning the genes encoding the CYP-450s, and the genetic engineering of suitable cells for heterologous expression, have provided new cell lines for studies on drug metabolism in vitro, under highly defined conditions. The V79 cell line, derived from Chinese hamster lung fibroblasts, was found to be suitable for heterologous expression, as these cells themselves do not express CYP-450s, thus providing a clean background for genetically engineering for the stable expression of any cloned CYP-450. In this way, V79 cell lines were created which specifically express CYP-450s from human, mouse, rat, and fish. These recombinant V79 cells have been applied in several drug metabolism and toxicity studies.

Mutagenesis of important amino acid reveals unconventional homologous internalization of beta(1)-adrenergic receptor.

AIMS: The study was designed to examine the internalization of Asp104Lys mutant of beta(1)-adrenergic receptor (beta(1)-AR) and compared to other mutant (Asp104Ala) and wild type receptors. Moreover, this study needs to perform the role of GRK2 (betaARK1) and beta-arrestin1 on this internalization of Asp104Lys mutant of beta(1)-AR. MAIN METHODS: Binding affinity, functional potency of agonist and agonist-induced internalization were determined for wild type and both mutants of beta(1)-ARs stably expressed in HEK 293 cells as assessed by [(3)H] CGP12177 radioligand. We have performed GRK2 and beta-arrestin1 expression levels by western blot analysis and also performed internalization of this mutant receptor after over expression and deletion of beta-arrestin1 gene. KEY FINDINGS: In the present study, the binding affinity of (-)-isoproterenol for both mutants were significantly decreased compared to wild type. Though the mutant Asp104Ala showed agonist-induced receptor activation, interestingly this mutant was not internalized. However, the mutant Asp104Lys, which showed uncoupling with G protein, was internalized 31.77+/-3.13% from cell surface. Asp104Lys mutant produced the same level of GRK2 expression in (-)-isoproterenol induced stimulation of wild type receptor and addition of (-)-isoproterenol further increased GRK2 expression in mutant receptors. In addition, overexpression of beta-arrestin1 in mutant Asp104Lys promoted (39.75+/-2.19%) and knockdown of beta-arrestin1 by siRNA decreased (3.55+/-1.75%) internalization compared to Asp104Lys mutant of beta(1)-ARs. SIGNIFICANCE: The present studies suggest that Asp104Lys mutant beta(1)-ARs triggers unconventional homologous internalization induced by G protein independent signals, where GRK2 and beta-arrestin1 play an important role for beta(1)-AR internalization.

Preparation and evaluation of self-nanoemulsifying tablets of carvedilol.

The purpose of this study was to combine the advantages of self-nanoemulsifying drug delivery systems and tablets as a conventional dosage form emphasizing the excipients' effect on the development of a new dosage form. Systems composed of HCO-40, Transcutol HP, and medium-chain triglyceride were prepared. Essential properties of the prepared systems regarding carvedilol solubility, a model drug, and self-emulsification time were determined. In order to optimize self-nanoemulsifying drug delivery systems (SNEDDS), formulation dispersion-drug precipitation test was performed in the absence and presence of cellulosic polymers. Furthermore, SNEDDS was loaded onto liquisolid powders. P-glycoprotein (P-gp) activity of the selected SNEDDS was tested using HCT-116 cells. Carvedilol showed acceptable solubility in the selected excipients. It also demonstrated improvement in the stability upon dilution with aqueous media in the presence of cellulosic polymers. Use of granulated silicon dioxide improved the physical properties of liquisolid powders containing SNEDDS. It improved the compressibility of the selected powders and the tested SNEDDS showed marked P-gp inhibition activity. Prepared self-nanoemulsifying tablet produced acceptable properties of immediate-release dosage forms and expected to increase the bioavailability of carvedilol.

Effects of dexamethasone and colostrum feeding on mRNA levels and binding capacities of beta-adrenergic receptors in the liver of neonatal calves.

Glucocorticoids increase plasma glucose concentrations in neonatal calves, but not hepatic gluconeogenic enzyme mRNA levels and activities. Catecholamines, too, enhance plasma glucose levels and regulate hepatic glucose metabolism. We have measured hepatic mRNA levels of beta-adrenergic receptors and beta-adrenergic receptor binding in neonatal calves on day 5 of life. Calves were fed either colostrums (C) or an isoenergetic milk-based formula (F), and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/(kg body weightday)). Abundance of mRNA was highest (P < 0.01) for beta2-adrenergic receptors and was higher (P < 0.01) for beta1- than for beta3-adrenergic receptors. DEXA treatment decreased (P < 0.05) beta1- and beta2-adrenergic receptor mRNA levels. Beta3-adrenergic receptor mRNA levels were higher (P < 0.05) in colostrum- than in formula-fed calves. Competitive binding revealed highest affinities for alprenolol, propranolol (both beta1- and beta2-antagonists), and ICI-188,551 (beta2-antagonist), which did not significantly differ from each other. Atenolol (beta1-antagonist) up to 10(-5) M did not displace (3H)-CGP-12177 from receptors. Competitive binding for adrenaline was best fitted by a two-receptor model. DEXA decreased (P < 0.05) (3H)-CGP-12177 binding capacities, whereas binding affinity of (3H)-CGP-12177 was not affected by DEXA or different feeding. Binding sites correlated positively with mRNA levels of beta2-adrenergic receptors (r = 0.56; P < 0.01). In conclusion, beta2-adrenergic receptors were the dominant subtype in the hepatic tissue. Feeding did not significantly affect beta2-adrenergic binding sites. However, DEXA decreased beta2-adrenergic binding sites and this was regulated at the transcriptional level.

[Study on the interactions between Ligusticum chuanxiong extract and cardiac muscle membrane receptors by CMSP chromatography].

OBJECTIVE: To study the interactions between Ligusticum chuanxiong Hort extract and cardiac muscle membrane receptors. METHOD: The cell membrane of rabbit cardiac muscle was fixed on silicon to make cell membrane stationary phase (CMSP), and then the interactions were studied by comparing the retention characteristics of the extracts from different solvents with those of the antagonists or activators corresponding to known receptors in cardiac muscle membrane, and by competition effect on the retention characteristics of extracts when adding the antagonists or activators into the mobile phase. RESULT: Water extract and ethanol extract both had retentions on CMSP; the retention characteristics of water extract could be affected when water extract was in competition with the antagonists for alpha receptor, and could not be affected when with the activator beta1 receptor. CONCLUSION: It is possible that some components in water extract may combine with alpha receptor and no component with beta1 receptor, and that some components in ethanol extract may combine with cardiac muscle cell membrane. The process between active components and receptors in vivo can be imitated through the interactions between drugs and CMSP. The method provides references for the resolution of two applications: to screen the active components from Chinese medicine, and to figure out the type of receptors involved.

Functional responses of human beta1 adrenoceptors with defined haplotypes for the common 389R>G and 49S>G polymorphisms.

OBJECTIVES: The human beta1-adrenoceptor (beta1-AR) is an important therapeutic target for cardiovascular diseases and has two common functional polymorphisms (49S>G and 389R>G). These polymorphisms have only been studied in isolation, however, and not in the context of the four haplotypes (SR, SG, GR and GG) that exist in native beta1-ARs. METHODS: To address this, the function of each of the receptor haplotypes was studied in HEK 293 cells stably transfected with appropriately modified human beta1-adrenoceptor cDNA sequence. RESULTS: The affinity for the beta-adrenoceptor ligand, [125I]-cyanopindolol, was not significantly different across the haplotypes, but a high affinity state for the beta1-AR could only be demonstrated for receptors carrying the 389R substitution. Both basal (GR 36.3 +/- 2.9* vs. SR 16.5 0 +/- 3.6 and GG 31.7 +/- 1.4* vs. SG 15.6 +/- 1.5 pmol/mg protein; *P < 0.001) and maximal (GR 163 +/- 7.6 vs. SR 124 +/- 8.1* and GG 75.0 +/- 1.0 vs. SG 52.4 +/- 1.1* pmol/mg protein; *P < 0.001) isoprenaline-evoked cAMP production was significantly affected by both substitutions. Incubation with isoprenaline (10 microm for 30 min or 20 h) caused increased down-regulation of beta1-ARs in cells expressing GG and GR haplotypes (at 20 h percentage fall respectively -28.1 +/- 5.2 and -38.2 +/- 3.0). CONCLUSIONS: These data highlight important functional differences between the common beta1-AR haplotypes and the need for consideration of haplotypes and not individual genotypes in determining the in-vivo role of these polymorphisms within this important drug target.

Screening drugs for metabolic stability using pulsed ultrafiltration mass spectrometry.

A pulsed ultrafiltration-mass spectrometric screening method has been developed to evaluate the metabolic stability of drugs. Pooled human liver microsomes containing cytochrome P450 enzymes were trapped by an ultrafiltration membrane in a stirred flow-through chamber, and eight beta-blocker drugs including acebutolol, alprenolol, atenolol, metoprolol, oxprenolol, pindolol, propranolol, and timolol were flow-injected through the chamber along with the cofactor NADPH. The ultrafiltrate was collected, concentrated and analyzed by using liquid chromatography-tandem mass spectrometry (LC-MS-MS) in order to quantitate the unmetabolized fraction of each drug. The metabolic stability of each beta-blocker was determined based on the difference between the corresponding LC-MS-MS peak areas of an experimental incubation and a control without NADPH. A flow-through incubation method, pulsed ultrafiltration metabolic screening minimizes the potential for product feed back inhibition of cytochrome P450 enzymes. The importance of this phenomenon was illustrated by the observation that the metabolic stability of the set of beta-blocker drugs measured using pulsed ultrafiltration more closely resembled the in vivo stability than that determined using a conventional batch incubation with microsomes or an incubation with human hepatocytes. Since a mixture of compounds was analyzed, the relative metabolic stability of each compound could be assessed by comparison to the other compounds in the incubation. This approach might be particularly useful for the ranking of a directed library of drug leads with respect to metabolic stability and then the selection of lead compounds for further drug development.

Heterologous expression of cytochrome P450 2D6 mutants, electron transfer, and catalysis of bufuralol hydroxylation: the role of aspartate 301 in structural integrity.

Cytochrome P450 (P450) 2D6 is a polymorphic human enzyme involved in the oxidation of >50 drugs, most of which contain a basic nitrogen. In confirmation of previous work by others, substitutions at Asp301 decreased rates of substrate oxidation by P450 2D6. An anionic residue (Asp, Glu) at this position was found to be important in proper protein folding and heme incorporation, and positively charged residues were particularly disruptive in bacterial and also in baculovirus expression systems. Truncation of 20 N-terminal amino acids had no significant effect on catalytic activity except to attenuate P450 2D6 interaction with membranes and NADPH-P450 reductase. The truncation of the N-terminus increased the level of bacterial expression of wild-type P450 2D6 (Asp301) but markedly reduced expression of all codon 301 mutants, including Glu301. Reduction of ferric P450 2D6 by NADPH-P450 reductase was enhanced in the presence of the prototypic substrate bufuralol. Bacterial flavodoxin, an NADPH-P450 reductase homolog, binds tightly to P450 2D6 but is inefficient in electron transfer to the heme. These results collectively indicate that the acidic residue at position 301 in P450 2D6 has a structural role in addition to any in substrate binding and that the N-terminus of P450 2D6 is relatively unimportant to catalytic activity beyond a role in facilitating binding to NADPH-P450 reductase.

A new aspect of view in synthesizing new type beta-adrenoceptor blockers with ancillary antioxidant activities.

A series of vanilloid-type beta-adrenoceptor blockers derived from antioxidant traditional Chinese herbal medicines were synthesized and tested for their antioxidant and adrenoceptor antagonistic activities. They all possessed significant beta-adrenoceptor blocking activities under in vitro experiments and radioligand binding assays. In addition, some compounds were further examined in in vivo tests and produced antagonist effects matching that of propranolol and labetalol by measurements of antagonism toward (-)isoproterenol-induced tachycardia and (-)phenylephrine-induced pressor responses in anesthetized rats. Furthermore, all of the compounds had antioxidant effects inherited from their original structures. In conclusion, compound 11 had the most potent beta-adrenoceptors blocking activity, 12 and 13 possessed high cardioselectivity, whereas 14, 15 and 16 possessed additional alpha-adrenoceptor blocking activity and 15 is the most effective antioxidant of all. The antioxidant activity may be due to their alpha and beta unsaturated side chain at position 1 and ortho-substituted methoxy moiety on 4-phenoxyethylamine.

The effect of melanotropic peptides on binding of [(3)H]dihydroalprenolol-hydrochloride to hypothalamic membranes.

In the present work we studied the interaction of alpha-melanocyte-stimulating hormone (alpha-MSH) and ACTH-(1-24) with beta-adrenergic receptors in hypothalamic membranes from rat brain. Saturation curves for [(3)H]dihydroalprenolol-hydrochloride ([(3)H]DHA) binding in the presence of the peptides revealed a decreased binding capacity (Bmax). The dissociation constant (Kd) was, however, not affected by alpha-MSH or ACTH-(1-24). These data indicate a non competitive interaction between these melanocortin peptides and [(3)H]DHA on beta-adrenergic receptors in hypothalamic membranes.

Evidence that oestradiol attenuates beta-adrenoceptor function in the hypothalamus of female rats by altering receptor phosphorylation and sequestration.

Activation of beta-adrenoceptors in the hypothalamus (HYP) and preoptic area (POA) inhibits both gonadotropin release and reproductive behaviour in female rats. Exposure of female rats for 48 h to physiologically relevant doses of oestrogen attenuates beta-adrenoceptor function in the HYP and POA as indicated by reduced isoproterenol (beta-adrenoceptor agonist) stimulation of adenylyl cyclase activity. Reduced beta-adrenoceptor coupling to G protein in the HYP-POA from oestrogen-exposed female rats correlates with attenuation of beta-adrenoceptor function. To examine potential mechanisms underlying receptor-G protein uncoupling, initial experiments tested the hypothesis that oestrogen attenuation of beta-adrenoceptor function in the HYP and POA involves receptor phosphorylation. Activation of endogenous serine/threonine phosphatases with protamine restores agonist-stimulated cAMP accumulation in HYP slices from oestrogen-exposed female rats to control levels. Additional experiments examined whether oestrogen-induced changes in beta-adrenoceptor binding density and/or subcellular localization correlate with the attenuation of beta-adrenoceptor function in the HYP and POA. Oestrogen treatment does not alter total beta-adrenoceptor binding density in the HYP or POA. However, oestrogen significantly reduces cell surface binding of the hydrophilic beta-adrenoceptor antagonist [3H] CGP 12177 to intact HYP and POA slices. At the same time, oestrogen decreases the fraction of beta-adrenoceptors localized in a light vesicle fraction following sucrose density gradient centrifugation. Therefore, oestrogen attenuates beta-adrenoceptor signalling in the HYP-POA by uncoupling the beta-adrenoceptor from G protein, perhaps by promoting receptor phosphorylation. Furthermore, a significant fraction of beta-adrenoceptors in the HYP and POA are no longer accessible to hydrophilic ligands, but are not internalized. Thus, physiological doses of oestrogen may facilitate reproductive behaviour and gonadotropin release, in part, by stabilizing beta-adrenoceptor phosphorylation in the HYP and POA, thereby uncoupling the receptors from G protein.

Regional brain distribution of noradrenaline uptake sites, and of alpha1-alpha2- and beta-adrenergic receptors in PCD mutant mice: a quantitative autoradiographic study.

The mouse "Purkinje cell degeneration" (pcd) is characterized by a primary loss of Purkinje cells, as well as by retrograde and secondary partial degeneration of cerebellar granule cells and inferior olivary neurons; this neurological mutant can be considered as an animal model of human degenerative ataxia. To determine the consequences of this cerebellar pathology on the noradrenergic system, noradrenaline transporters as well as alpha1-, alpha2- and beta-adrenergic receptors were evaluated by quantitative ligand binding autoradiography in adult control and pcd mice using, respectively, [3H]nisoxetine, [3H]prazosin, [3H]idazoxan and [3H]CGP12177. In cerebellar cortex and deep nuclei of pcd mutants, [3H]nisoxetine labelling of noradrenaline transporters was higher than in control mice. However, when binding densities were corrected by surface area, they remained unchanged in the cerebellar cortex but associated with 25% and 40% lower levels of labelling of alpha1 and beta receptors, as well as a very important increase (275%) of alpha2 receptors. In deep cerebellar nuclei, surface corrections did not reveal any changes either in transporter or in receptor densities. Higher densities of [3H]nisoxetine labelling were found in several regions related with the cerebellum, namely inferior olive, inferior colliculus, vestibular, reticular, pontine, raphe and red nuclei, as well as in primary motor and sensory cerebral cortex; they may reflect an increased noradrenergic innervation related to motor adjustments for the cerebellar dysfunction. Increased [3H]nisoxetine labelling was also measured in vegetative brainstem regions and in dorsal hypothalamus, implying altered autonomic functions and possible compensation in pcd mutants. Other changes found in extracerebellar regions affected by the mutation, such as thalamus and the olfactory system implicated both noradrenaline transporters and adrenergic receptors. In contrast to the important alterations of the noradrenergic system in cerebellar cortex, the lack of receptor changes in deep cerebellar nuclei suggests that local adaptations may be sufficient to minimize the consequence of the cerebellar atrophy on motor control. An intense labelling by [3H]idazoxan of the inner third of the molecular layer was a novel, albeit unexplained finding, and could represent a postsynaptic subset of alpha2-adrenergic receptors.

Effect of the Yang tonifying herbs on myocardial beta-adrenoceptors of hypothyroid rabbits.

New Zealand White female rabbits were randomly divided into three groups, each contained six rabbits, i.e. thyroidectomized and untreated rabbits (group 1), thyroidectomized rabbits treated by the Yang tonifying herbs (group 2) and sham thyroidectomized rabbits as controls (group 3). The myocardial beta-adrenoceptor density (Bmax) and affinity (Kd) of each group of rabbits were determined by radioligand binding assay technique on the thirtieth postoperative day and the data were handled by using a computer program of the Woolf plot with weight regression. Moreover, the serum levels of thyroxine (T4) and triiodothyronine (T3) of each group of rabbits were measured by radioimmunoassay technique and their heart rates (HR) were also recorded on the preoperative and thirtieth postoperative day. The results showed that the Bmax, T4, T3 and HR in group 1 were lower significantly than that in group 3 (P < 0.01-0.001), but the change of Kd in group 1 was not significant; the deviation of the indices from the normal value in group 2 was less remarkably than in group 1 other than T4.

Using capillary electrophoresis/frontal analysis to screen drugs interacting with human serum proteins.

We have used capillary electrophoresis in the frontal analysis mode (CE/FA) to determine the binding capacity of beta-adrenoceptor blocking drugs to individual serum proteins, serum protein mixtures and human serum. The free drug concentration was directly measured from the height of the frontal peak and used to calculate the bound drug concentration. From the bound drug concentration, the percentage of drug bound to the serum proteins alpha1-acid glycoprotein (AGP) and human serum albumin (HSA) was then determined. In addition to determining the percent of a drug bound to a protein, the drug-protein association constant (Ka) was determined for AGP binding to beta-blockers. The data-estimated association constants were consistent with literature values. The CE/FA studies on the beta-adrenoceptor blocking drugs and the serum proteins indicated that HSA, AGP, high density lipoprotein (HDL), and low density lipoprotein (LDL) were the main contributors to serum binding for this series of compounds. The serum-drug binding data sorted the beta-adrenoceptor blocking drugs into high and low binding categories. The protein mixture (AGP + HSA + HDL + LDL) resulted in dividing the beta-blockers into the same high/low rankings. The protein mixture (AGP + HSA + HDL + LDL) was amenable to automation, did not autoaggregate, and had constant concentrations for the proteins.

Evidence for altered central noradrenergic function in experimental acute liver failure in the rat.

These is increasing evidence to suggest that central noradrenergic mechanisms may contribute to the central nervous system manifestations of acute liver failure. To further elucidate this possibility, extracellular brain concentrations of the monoamines, noradrenaline (NA), dopamine (DA), and serotonin, were measured by high-performance liquid chromatography with electrochemical detection in microdialysates from the extracellular compartment of frontal cortex in rats with acute (ischemic) liver failure at various times during the progression of encephalopathy and brain edema, as well as in obligate control groups of animals. In addition, binding sites for the noradrenergic receptor subtype ligands, [3H]-prazosin (alpha1 sites), [3H]-RX821002 (alpha2 sites), and [125]I-iodopindolol (beta sites), were assessed using quantitative receptor autoradiography in regions of the brains of rats at coma stage of acute liver failure and of control groups of animals. Coma stages of encephalopathy in acute liver failure were associated with selectively increased noradrenaline concentrations (P < .05) and a concomitant selective loss of alpha1 and beta1 sites in frontal cortex and thalamus. These findings add to a growing body of evidence that central noradrenergic function is modified in acute liver failure and suggest that alpha1/beta1 receptor-mediated noradrenergic mechanisms may play a role in the pathogenesis of brain edema and encephalopathy in this condition.

Antimigraine drug interactions with serotonin receptor subtypes in human brain.

The interactions of antimigraine agents with serotonin (5-hydroxytryptamine, 5-HT) receptor subtypes were analyzed in human frontal cortex membranes. The drugs studied included 5-HT antagonists, beta-adrenergic antagonists, and calcium channel blockers. At 5-HT1A sites labeled by 3H-8-hydroxy-2-(N,N-dipropylamino)-tetralin, (-)pindolol, alprenolol, (-)propranolol, methysergide, cyproheptadine, and pizotifen are similar in that they display affinities of approximately 100 nM for this receptor. By contrast, only methysergide displays relatively high affinity (120 +/- 60 nM), whereas all other drugs have affinities greater than 1,000 nM for non-5-HT1A sites labeled by 3H-5-HT in human cortex. Finally, at 5-HT2 receptors labeled by 3H-spiperone, cyproheptadine, methysergide, and pizotifen are extremely potent agents (affinity constants of 1 to 10 nM), whereas amitriptyline (23 +/- 4 nM), verapamil (140 +/- 50 nM), and nifedipine (320 +/- 80 nM) are moderately potent. All other drugs are inactive at concentrations below 1,000 nM. These data demonstrate that most antimigraine drugs display high affinity for the 5-HT1A and/or 5-HT2 receptor subtypes in human brain. However, antimigraine efficacy cannot be explained by drug interactions with a single 5-HT receptor subtype.

Selection of optimal drug therapy for the patient with angina pectoris.

The development of new drugs, especially beta-blocking and calcium entry-blocking agents, has greatly facilitated the medical treatment of angina pectoris. The specific needs of each patient should dictate the appropriate treatment of angina pectoris. Angina may occur in patients who have various concomitant disorders such as hypertension, diabetes mellitus, peripheral vascular disease, chronic obstructive pulmonary disease, or arrhythmias, and the physician must take these factors into account when a drug regimen is prescribed. Individual drugs should be chosen on the basis of specifically desired pharmacologic effects, and the dosages should be gradually adjusted according to the patient's response. Although a therapeutic regimen should be selected primarily on the basis of efficacy, the physician must also attempt to recommend a simple and cost-effective program.