Endogenous Catecholamines Research Articles

Altered neutrophil-to-lymphocyte ratio in sepsis secondary to canine parvoviral enteritis treated with and without an immunomodulator in puppies.

Neutrophil-to-lymphocyte ratio (NLR) is a cheap and easy-to-obtain biomarker that mirrors the balance between innate and adaptive immunity. Cortisol and catecholamines have been identified as major drivers of NLR. High cortisol levels increase neutrophils while simultaneously decreasing lymphocyte counts. Likewise, endogenous catecholamines may cause leukocytosis and lymphopenia. Thus, NLR allows us to monitor patient severity in conditions such as sepsis. Twenty-six puppies with sepsis secondary to canine parvoviral enteritis were treated with and without an immunomodulator. Our group determined the NLR and the plasmatic cortisol levels by chemiluminescence, and norepinephrine (NE) and epinephrine (E) by HPLC during the first 72 h of clinical follow-up. Our results showed that at admission puppies presented an NLR value of 1.8, cortisol of 314.9 nmol/L, NE 3.7, and E 3.3 pmol/mL. Both treatments decreased admission NLR values after 24 h of treatment. However, only the puppies treated with the immunomodulator (I) remained without significant changes in NLR (0.7-1.4) compared to the CT group, and that showed a significant difference (P < 0.01) in their NLR value (0.4-4.6). In addition, we found significant differences in the slope values between the admission and final values of NLR (P < 0.005), cortisol (P < 0.02), and E (P < 0.05) between treatments. Then, our data suggest that the immunomodulator positively affects the number of lymphocytes and neutrophils involved in NLR as well as major drivers like cortisol and epinephrine, which is reflected in clinical parameters and survival.

Catecholamine Toxicity After Craniotomy Evacuation Craniotomy and Evacuation of The Abscess

Increasing levels of endogenous catecholamines occur acutely to provide short-time adaptation to stressful conditions, known as the fight-or-fly response. Catecholamine toxicity requires multidisciplinary management. In this case, the patient is diagnosed with a brain abscess since birth. According of the history, physical examination and investigations, it was concluded that the diagnosis of epidural abscess with abscess evacuation craniotomy and PS ASA 2 (leukocytosis) with GA-ETT anesthesia. The operation is carried out with a duration of 4 hours. Vital sign monitoring obtained blood pressure sp108 – 125 62 - 90 mmHg, heart frequency 90 - 120 times per minute, 99% oxygen saturation. When in the recovery room, the patient experiences cardiac arrest, this is thought to result from catecholamine toxicity. Patients are treated as resuscitation in accordance with the algorithm of cardiac arrest in children. Patients experienced a response of spontaneous circulation (ROSC) and performed vital sign monitoring.

Classification, pathophysiology and principle of therapy of shock

Shock is a clinical syndrome that results from lack of oxygen utilization or supply to vital organs resulting in hypoxia. Shock is associated with significant morbidity and mortality as if not treated timely can lead to multiple organ failure and death. The mortality rate of shock ranges from 20% to 50%. Shock has several pathophysiologies including intracardiac etiologies such as myocardial infarction, myopathy, or severe arrhythmia which produce altered maturation and cause heart failure while loss of internal or external fluid due to trauma or bleeding often results in hypovolemia. Also, obstruction by extracardiac causes and activation of inflammatory cascade can induce shock. The purpose of this research is to review the available information about the classification, pathophysiology and principle of therapy of shock. The major classification of shock includes cardiogenic, hypovolemic, obstructive and distributive shock. Distributive shock is further divided into three subclasses of septic, anaphylactic and neurogenic shock. Haemorrhagic shock is also the sub-type of hypovolemic shock. Each class of shock requires a specific treatment and timely management to prevent any further complications. Constant examination, resuscitation and re-evaluation are important in therapy of shock. To treat hypotension and to increase cardiac output, vasopressor drugs and inotropic adrenergic drugs continue to be the most widely used therapies. Endogenous catecholamines such as epinephrine, norepinephrine, and dopamine among other vasopressors have been shown to be effective in treating various types of shocks that are controlled as part of treatment for shock. Early diagnosis and prompt treatment can help in prevention of complications of shock also enhancing the recovery of patients.

Epinephrine evokes shortening of human airway smooth muscle cells following β2 adrenergic receptor desensitization.

Epinephrine (EPI), an endogenous catecholamine involved in the body’s fight-or-flight responses to stress, activates α1-adrenergic receptors (α1ARs) expressed on various organs to evoke a wide range of physiological functions, including vasoconstriction. In the smooth muscle of human bronchi, however, the functional role of EPI on α1ARs remains controversial. Classically, evidence suggests that EPI promotes bronchodilation by stimulating β2-adrenergic receptors (β2ARs). Conventionally, the selective β2AR agonism of EPI was thought to be, in part, due to a predominance of β2ARs and/or a sparse, or lack of α1AR activity in human airway smooth muscle (HASM) cells. Surprisingly, we find that HASM cells express a high abundance of ADRA1B (the α1AR subtype B) and identify a spontaneous “switch-like” activation of α1ARs that evokes intracellular calcium, myosin light chain phosphorylation, and HASM cell shortening. The switch-like responses, and related EPI-induced biochemical and mechanical signals, emerged upon pharmacological inhibition of β2ARs and/or under experimental conditions that induce β2AR tachyphylaxis. EPI-induced procontractile effects were abrogated by an α1AR antagonist, doxazosin mesylate (DM). These data collectively uncover a previously unrecognized feed-forward mechanism driving bronchospasm via two distinct classes of G protein-coupled receptors (GPCRs) and provide a basis for reexamining α1AR inhibition for the management of stress/exercise-induced asthma and/or β2-agonist insensitivity in patients with difficult-to-control, disease subtypes.

Evaluation of changes in Blood Pressure (BP) and Heart Rate (HR) among controlled Hypertensive and Normotensive Patients before and after receiving Dental Local Anesthesia (DLA) with Adrenaline: A Prospective Study

To evaluate the alterations in blood pressure (BP) and heart rate (HR) among hypertensive and normotensive patients receiving dental local anesthesia using 2% lidocaine with epinephrine. This prospective observational study was carried out at the College of Dentistry, Jazan, KSA. A total of 40 adult patients were included in the study. They were divided into two groups (n=20). Group “A” included normotensive patients and group “B” included controlled hypertensive patients. The BP and HR were measured by a sphygmomanometer and pulse oximeter in three different temporal locations: on arrival to the waiting room, and in clinic before and after administration of local anesthesia. The mean values of the measurements in the three locations; the waiting area, clinic before and after the administration of DLA, were noted. The only significant alterations were found in the Systolic Blood Pressure (SBP) of both hypertensive and normotensive patients before the administration of DLA and in the HR of hypertensive patients again only before the administration of DLA. Endogenous catecholamines are more significant in causing hemodynamic disturbances in dental patients. Hypertensive patients seem to be more vulnerable to these disturbances.

Chest compressions and medications during neonatal resuscitation

Prolonged resuscitation in neonates, although quite rare, may occur in response to profound intractable bradycardia as a result of asphyxia. In these instances, chest compressions and medications may be necessary to facilitate return of spontaneous circulation. While performing chest compressions, the two thumb method is preferred over the two finger technique, although several newer approaches are under investigation. While the ideal compression to ventilation ratio is still uncertain, a 3:1 ratio remains the recommendation by the Neonatal Resuscitation Program. Use of feedback mechanisms to optimize neonatal cardiopulmonary resuscitation (CPR) show promise and are currently under investigation. While performing optimal cardiac compressions to pump blood, use of medications to restore spontaneous circulation will likely be necessary. Current recommendations are that epinephrine, an endogenous catecholamine be used preferably intravenously or by intraosseous route, with the dose repeated every 3-5 minutes until return of spontaneous circulation. Finally, while the need for volume replacement is rare, it may be considered in instances of acute blood loss or poor response to resuscitation.

Transient ventricular bigeminy during emergence from general anesthesia in a pediatric patient with catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare genetic disease that is characterized by ventricular arrhythmias and sudden death, induced by exogenous and endogenous catecholamine. We performed general anesthesia for dental treatment of multiple teeth in a 7-year-old boy with CPVT. To avoid sympathetic tone, anesthesia was maintained by total intravenous anesthesia, but ventricular bigeminy was induced by stimulation on emergence form general anesthesia. Although bigeminy in the present case might have been less likely to induce a fatal arrhythmia, we should keep in mind that a small amount of sympathetic tone may induce arrhythmias in a patient with CPVT.

Perioperative Supplemental Oxygen and Plasma Catecholamine Concentrations after Major Abdominal Surgery-Secondary Analysis of a Randomized Clinical Trial.

Perioperative stress is associated with increased sympathetic activity that leads to increases in heart rate and blood pressure, which are associated with the development of perioperative myocardial ischemia. In healthy volunteers, it was shown that the administration of supplemental oxygen attenuated sympathetic nerve activity and subsequently led to lower plasma catecholamine concentrations. We therefore tested the hypothesis that perioperative supplemental oxygen attenuates sympathetic nerve in patients at risk for cardiovascular complications undergoing major abdominal surgery. We randomly assigned 81 patients to receive either 80% or 30% inspired oxygen concentration throughout surgery and the first two postoperative hours. We assessed noradrenaline, adrenaline, and dopamine plasma concentrations before the induction of anesthesia, two hours after surgery and on the third postoperative day. There was no significant difference in postoperative noradrenaline (effect estimated: −41.5 ng·L−1, 95%CI −134.3, 51.2; p = 0.38), adrenaline (effect estimated: 11.2 ng·L−1, 95%CI −7.6, 30.1; p = 0.24), and dopamine (effect estimated: −1.61 ng·L−1, 95%CI −7.2, 3.9; p = 0.57) concentrations between both groups. Based on our results, it seems unlikely that supplemental oxygen influences endogenous catecholamine release in the perioperative setting.

Adrenergic prolongation of action potential duration in rainbow trout myocardium via inhibition of the delayed rectifier potassium current, IKr

Catecholamines mediate the ‘fight or flight’ response in a wide variety of vertebrates. The endogenous catecholamine adrenaline increases heart rate and contractile strength to raise cardiac output. The increase in contractile force is driven in large part by an increase in myocyte Ca2+ influx on the L-type Ca current (ICaL) during the cardiac action potential (AP). Here, we report a K+- based mechanism that prolongs AP duration (APD) in fish hearts following adrenergic stimulation. We show that adrenergic stimulation inhibits the delayed rectifier K+ current (IKr) in rainbow trout (Oncorhynchus mykiss) cardiomyocytes. This slows repolarization and prolongs APD which may contribute to positive inotropy following adrenergic stimulation in fish hearts. The endogenous ligand, adrenaline (1 μM), which activates both α- and β-ARs reduced maximal IKr tail current to 61.4 ± 3.9% of control in atrial and ventricular myocytes resulting in an APD prolongation of ~20% at both 50 and 90% repolarization. This effect was reproduced by the α-specific adrenergic agonist, phenylephrine (1 μM), but not the β-specific adrenergic agonist isoproterenol (1 μM). Adrenaline (1 μM) in the presence of β1 and β2-blockers (1 μM atenolol and 1 μM ICI-118551, respectively) also inhibited IKr. Thus, IKr suppression following α-adrenergic stimulation leads to APD prolongation in the rainbow trout heart. This is the first time this mechanism has been identified in fish and may act in unison with the well-known enhancement of ICaL following adrenergic stimulation to prolong APD and increase cardiac inotropy.

Targeting Catecholamines to Develop New Drugs for Attention Deficit Hyperactivity Disorder

The prevalence of attention deficit hyperactivity disorder (ADHD), a developmental neuropsychiatric disorder, is high among children and adolescents. The pathogenesis of ADHD is mediated with genetic, biological, and environmental factors. Most therapeutic drugs for ADHD have so far targeted biological causes, primarily by regulating catecholaminergic neurotransmitters. However, ADHD drugs that are clinically treated have various problems in their addictiveness and drug stability; thus, it is recommended that efficacy and safety should be secured through simultaneous prescription of multiple drugs rather than a single drug treatment. Accordingly, it is necessary to develop drugs that newly target pathogenic mechanisms of ADHD. In this study, we attempt to confirm the possibility of developing new drugs by reviewing dopamine-related developmental mechanisms of neurons and their correlation with ADHD. Histone deacetylase inhibitors (HDACi) can regulate the concentration of intracellular dopamine in neurons by expressing vesicular monoamine transporter 2 and inducing the exocytosis of neurotransmitters to the synaptic cleft, thereby promoting the development of neurons and signal transmission. This cellular modulation of HDACi is expected to treat ADHD by regulating endogenous catecholamines such as dopamine. Although studies are still in the preclinical stage, HDAC inhibitors clearly have potential as a therapeutic agent with low addictiveness and high efficacy for ADHD treatment.

Clinical Update on Vasopressors and Titration Strategies.

Clinical Update on Vasopressors and Titration Strategies.

A Pilot Study on the 1H-NMR Serum Metabolic Profile of Takotsubo Patients Reveals Systemic Response to Oxidative Stress

Takotsubo syndrome (TTS) presents as an acute coronary syndrome characterized by severe left ventricular (LV) dysfunction and non-obstructive coronary artery disease that typically shows spontaneous recovery within days or weeks. The mechanisms behind TTS are mainly related to beta-adrenergic overstimulation and acute endogenous catecholamine surge, both of which could increase oxidative status that may induce further deterioration of cardiac function. Although several studies reported evidence of inflammation and oxidative stress overload in myocardial tissue of TTS models, systemic biochemical evidence of augmented oxidant activity in patients with TTS is lacking. In this study, serum samples of ten TTS patients and ten controls have been analyzed using 1H-NMR spectroscopy. The results of this pilot study show a marked alteration in the systemic metabolic profile of TTS patients, mainly characterized by significant elevation of ketone bodies, 2-hydroxybutyrate, acetyl-L-carnitine, and glutamate levels, in contrast with a decrease of several amino acid levels. The overall metabolic fingerprint reflects a systemic response to oxidative stress caused by the stressor that triggered the syndrome’s onset.

Abstract 13411: Vasodilatory Capacity With Regadenoson Myocardial Perfusion Imaging In Patients With End Stage Liver Disease

Introduction: The sensitivity and specificity of myocardial perfusion imaging in end stage liver disease (ESLD) patients ranges between 35-37% and 63-88%, respectively. Despite high levels of endogenous catecholamines and angiotensin, ESLD induced arterial vasodilation may exhaust the vasodilatory capacity of common pharmacologic stress agents. Reduced heart rate (HR) response to vasodilator stress test has been associated with increased major adverse cardiac events (MACE) in pre-transplant end stage renal disease patients but there is limited data in ESLD. We hypothesize that the hemodynamic response, measured as a change in HR and systolic blood pressure (SBP), during regadenoson stress test will be more robust when associated with low level exercise. Method: Forty-five subjects with ESLD referred for pre-transplant risk stratification were assigned to 1 of 3 groups: regadenoson alone or associated with low level treadmill or bicycle maneuver. Regadenoson was injected 2 minutes after low level exercise in the treadmill and bicycle groups. Myocardial perfusion images and hemodynamic changes were performed and interpreted as part of the standard clinical protocol. Results: There were 21 subjects in the regadenoson alone group, 10 in the low level treadmill group, and 14 in the bicycle maneuver group. There were no perfusion abnormalities in any of the groups and LVEF were greater than 50%. There was a statistically significant difference in HR response between the 3 groups (p = 0.015), but not in percentage SBP change between the 3 groups (p = 0.4). Pairwise comparison of regadenoson alone vs. low level treadmill percentage HR change showed statistical significance (p = 0.011). There was no MACE at 6-month follow-up. Conclusions: Low level exercise achieved a higher HR response than the other groups with a similar SBP response. The increased HR response may represent a more physiologic assessment of the true vasodilatory capacity remaining in ESLD patients.

Application of beta-blockers in burn management

Severe burn injuries cause chronic inflammation, which produces a subsequent hypermetabolic response that starts immediately and persists for at least 3 years. The hypermetabolic state, which is thought to be due to postburn elevations of endogenous catecholamines and cortisol, is associated with a number of harmful physiologic derangements including immunosuppression, impaired wound healing, muscle catabolism, and hepatic dysfunction. Beta-blockers have become first line agents for reducing these adverse effects of hypermetabolism in severe burns. This review discusses the underlying pharmacological mechanisms demonstrated by clinical studies evaluating the safety and efficacy of beta-blockers in the management of burn injuries. A literature search was performed using the PubMed database to identify articles on beta-blockers and burn management. The review yielded 33 relevant results consisting of randomized controlled trials, original research articles, and meta-analyses in pediatric and adult burn patients. Propranolol administration reduced insulin resistance, lipolysis, proteolysis, cardiac work, and bone loss resulting from burn-associated hypermetabolism. Propranolol also effectively reduced myocardial stress, resting energy expenditure, and central deposition of fat. Recent studies have begun to evaluate incorporation of anabolic agents and rehabilitative exercise therapy. However, at this time propranolol continues to be the most effective therapy for reducing the hypermetabolic response and other morbidities resulting from burn injuries.

Comparative study of dexmedetomidine vs. midazolam on plasma catecholamine levels and hemodynamics in patients with septic shock

To compare the effects of dexmedetomidine (DEX) and midazolam on the endogenous plasma catecholamine levels and the dosage of exogenous norepinephrine (NE) to maintain blood pressure in patients with septic shock. From January 2018 to December 2019, patients admitted to the department of critical care medicine of the Affiliated Hospital of Guizhou Medical University who needed invasive mechanical ventilation and had a stay of more than 48 hours in the intensive care unit (ICU) for septic shock and received DEX or midazolam for sedation were enrolled in this study. The hemodynamic data, arterial blood lactic acid (Lac) level, arterial blood gas analysis and vasoactive drug dose at 0, 12, 24, 48, 72 hours after entering the ICU were dynamically recorded, and the plasma catecholamine levels at 0, 24, 48 hours after entering the ICU were recorded. The acute physiology and chronic health evaluation II (APACHE II) score and sequential organ failure assessment (SOFA) score on ICU-admission were calculated. The parameters of prognosis were collected. A total of 24 patients were enrolled, 12 in the DEX group and 12 in the midazolam group. There were similar dynamic trends in heart rate (HR), central venous pressure (CVP), venous-arterial carbon dioxide pressure difference (Pv-aCO2), oxygenation index (PaO2/FiO2), and Lac level of patients between the two groups. Only the 12-hour CVP and 72-hour Pv-aCO2 in the DEX group were significantly higher than those in the midazolam group [CVP (mmHg, 1 mmHg = 0.133 kPa): 13±3 vs. 10±3, Pv-aCO2 (mmHg): 9.4±5.2 vs. 4.8±2.2, both P < 0.05], and the mean arterial pressure (MAP) of patients in the DEX group at 48 hours and 72 hours was significantly higher than that in the midazolam group (mmHg: 95±10 vs. 86±10, 96±9 vs. 88±7, both P < 0.05). There was no statistically significant difference in the duration of mechanical ventilation, ICU mortality or in-hospital mortality between the DEX group and the midazolam group [duration of mechanical ventilation (days): 5.6 (3.8, 9.5) vs. 10.5 (5.9, 15.0), ICU mortality: 16.7% vs. 33.3%, in-hospital mortality: 25.0% vs. 41.7%, all P > 0.05]. There was no significant difference in the dosage of propofol or sufentanil between the DEX group and the midazolam group [propofol (mg/kg): 0 (0, 9.35) vs. 4.07 (0, 13.75), sufentanil (μg/kg): 6.26 (4.90, 9.80) vs. 8.32 (3.52, 9.34), both P > 0.05]. The levels of plasma NE, dopamine and dobutamine in the DEX group at 48 hours were significantly lower than those in the midazolam group [NE (ng/L): 1 850.12 (342.16, 2 938.05) vs. 4 596.60 (3 310.56, 5 546.84), dopamine (ng/L): 119.10 (60.47, 200.71) vs. 275.40 (214.61, 418.88), dobutamine (ng/L): 51.20 (36.85, 75.59) vs. 98.97 (85.65, 107.10), all P < 0.05], but the amount of NE required to maintain MAP between 65 mmHg and 75 mmHg in the DEX group and the midazolam group was similar [μg/kg: 1 922 (1 170, 4 887) vs. 2 466 (2 043, 3 438), P > 0.05]. DEX can reduce plasma catecholamine levels in patients with septic shock more than midazolam, and does not increase the dose of exogenous NE, and has a smaller effect on hemodynamics in patients with septic shock than midazolam.

Quality of Death in Fighting Bulls during Bullfights: Neurobiology and Physiological Responses.

Simple SummaryFighting bulls that participate in bullfighting face energy and metabolic demands due to the high intensity and duration of the exercise performed. Under these conditions, specific corporal mechanisms, such as the acid–base balance, are affected, causing metabolic acidosis. However, fighting bulls also undergo muscular injuries, physiological changes, and high enzyme concentrations that reflect the stress to which they are subjected, and in some bulls, bullfights can trigger electrolytic imbalances that include hypercalcaemia, hypermagnesaemia, and hyperphosphataemia, exacerbated by muscular necrosis and myoglobinuria.During bullfights, bulls undergo physiometabolic responses such as glycolysis, anaerobic reactions, cellular oedema, splenic contraction, and hypovolemic shock. The objective of this review article is to present the current knowledge on the factors that cause stress in fighting bulls during bullfights, including their dying process, by discussing the neurobiology and their physiological responses. The literature shows that biochemical imbalances occur during bullfights, including hypercalcaemia, hypermagnesaemia, hyperphosphataemia, hyperlactataemia, and hyperglycaemia, associated with increased endogenous cortisol and catecholamine levels. Creatine kinase, citrate synthase, and lactate dehydrogenase levels also increase, coupled with decreases in pH, blood bicarbonate levels, excess base, partial oxygen pressure, and oxygen saturation. The intense exercise also causes a marked decrease of glycogen in type I and II muscle fibres that can produce myoglobinuria and muscular necrosis. Other observations suggest the presence of osteochondrosis. The existing information allows us to conclude that during bullfights, bulls face energy and metabolic demands due to the high intensity and duration of the exercise performed, together with muscular injuries, physiological changes, and high enzyme concentrations. In addition, the final stage of the bullfight causes a slow dying process for an animal that is sentient and conscious of its surroundings.

Differential Susceptibilities of Catecholamines to Metabolism by Monoamine Oxidases.

The endogenous catecholamines dopamine (DA), norepinephrine (NE), and epinephrine (EPI) play key roles in neurobehavioral, cardiovascular, and metabolic processes; various clinical disorders; and effects of numerous drugs. Steps in intracellular catecholamine synthesis and metabolism were delineated long ago, but there remains a knowledge gap. Catecholamines are metabolized by two isoforms of monoamine oxidase (MAO), MAO-A and MAO-B, and although the anatomic localization of MAO-A and MAO-B and substrate specificities of enzyme inhibitors are well characterized, relative susceptibilities of the endogenous catecholamines to enzymatic oxidation by MAO-A and MAO-B have not been studied systematically. MAOs catalyze the conversion of catecholamines to catecholaldehydes-3,4-dihydroxyphenylacetaldehyde (DOPAL) from DA and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL) from NE and EPI. In this study we exploited the technical ability to assay DOPAL and DOPEGAL simultaneously with the substrate catecholamines to compare DA, NE, and EPI in their metabolism by MAO-A and MAO-B. For both MAO isoforms, DA was the better substrate compared to NE or EPI, which were metabolized equally. Since catecholaminergic neurons express mainly MAO-A, the finding that MAO-A is more efficient than MAO-B in metabolizing endogenous catecholamines reinforces the view that the predominant route of intraneuronal enzymatic oxidation of catecholamines is via MAO-A. The results have implications for clinical neurochemistry, experimental therapeutics, and computational models of catecholaminergic neurodegeneration. For instance, the greater susceptibility of DA than the other catecholamines to both MAO isoforms can help explain relatively high concentrations of the deaminated DA metabolite 3,4-dihydroxyphenylacetic acid than of the NE metabolite 3,4-dihydroxyphenylglycol in human plasma and urine. SIGNIFICANCE STATEMENT: Endogenous catecholamines are metabolized by monoamine oxidase (MAO)-A and -B, yielding the catecholaldehydes 3,4-dihydroxyphenylacetaldehyde (DOPAL) from dopamine (DA) and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL) from norepinephrine (NE) and epinephrine (EPI). Based on measurements of DOPAL and DOPEGAL production, DA is a better substrate than NE or EPI for both MAO isoforms, and MAO-A is more efficient than MAO-B in metabolizing DA, NE, and EPI. MAO-A is the main route of intraneuronal metabolism of endogenous catecholamines.

A word on netting of angiotensin-converting enzyme inhibitor therapy in hypoplastic left heart syndrome following stage-I.

NPC-QIC Registry data showed that angiotensin-converting enzyme inhibitors were described in almost 38% for patients with single ventricle physiology after stage-I Norwood palliation. However, mortality and ventricular dysfunction or atrioventricular valve insufficiency seems to be not improved by oral application of angiotensin-converting enzyme inhibitors. The final conclusion was that despite limited evidence of benefit for patients with hypoplastic left heart syndrome, prescription of angiotensin-converting enzyme inhibitors during interstage is still common. Taking into account of the predominant cardiovascular regulation in newborns and young infants by circulating catecholamines, no real improvement is to be expected from angiotensin-converting enzyme inhibitor monotherapy. The goals of drug therapy after stage-I Norwood palliation in hypoplastic left heart syndrome are prevention of systemic right ventricle failure, balancing pulmonary and systemic blood flow, and reduction of oxygen consumption with regard to limitations of oxygen supply by the single ventricle, furthermore, avoiding harmful effects of endogenous catecholamine production in the long term on somatic and cognitive development. In this light of knowledge, we want to recommend the use of a long-acting and highly specific ß1-adrenoreceptor blocker for almost all patients after stage-I Norwood palliation and a combination with angiotensin-converting enzyme inhibitors only by indication after exclusion of potential side effects.

β1-Blockers Enhance Inotropy of Endogenous Catecholamines in Chronic Heart Failure.

Although β1-blockers impressively reduce mortality in chronic heart failure (CHF), there are concerns about negative inotropic effects and worsening of hemodynamics in acute decompensated heart failure. May receptor theory dispel these concerns and confirm clinical practice to use β1-blockers? In CHF, concentrations of catecholamines at the β1-adrenoceptors usually exceed their dissociation constants (KDs). The homodimeric β1-adrenoceptors have a receptor reserve and display negative cooperativity. We considered the binomial distribution of occupied receptor dimers with respect to the interaction of an exogenous β1-blocker and elevated endogenous agonist concentrations > [KDs], corresponding to an elevated sympathetic tone. Modeling based on binomial distribution suggests that despite the presence of a low concentration of the antagonist, the activation of the dimer receptors is higher than that in its absence. Obviously, the antagonist improves the ratio of the dimer receptors with only single agonist activation compared with the dimer receptors with double activation. This leads to increased positive inotropic effects of endogenous catecholamines due to a β1-blocker. To understand the positive inotropic sequels of β1-blockers in CHF is clinically relevant. This article may help to eliminate the skepticism of clinicians about the use of β1-blockers because of their supposed negative inotropic effect, since, on the contrary, a positive inotropic effect can be expected for receptor-theoretical reasons.

Current Developments on the Role of α1-Adrenergic Receptors in Cognition, Cardioprotection, and Metabolism

The α1-adrenergic receptors (ARs) are G-protein coupled receptors that bind the endogenous catecholamines, norepinephrine, and epinephrine. They play a key role in the regulation of the sympathetic nervous system along with β and α2-AR family members. While all of the adrenergic receptors bind with similar affinity to the catecholamines, they can regulate different physiologies and pathophysiologies in the body because they couple to different G-proteins and signal transduction pathways, commonly in opposition to one another. While α1-AR subtypes (α1A, α1B, α1C) have long been known to be primary regulators of vascular smooth muscle contraction, blood pressure, and cardiac hypertrophy, their role in neurotransmission, improving cognition, protecting the heart during ischemia and failure, and regulating whole body and organ metabolism are not well known and are more recent developments. These advancements have been made possible through the development of transgenic and knockout mouse models and more selective ligands to advance their research. Here, we will review the recent literature to provide new insights into these physiological functions and possible use as a therapeutic target.