Citrus p-Synephrine Improves Energy Homeostasis by Regulating Amino Acid Metabolism in HFD-Induced Mice

p-Synephrine is a common alkaloid widely distributed in citrus fruits. However, the effects of p-synephrine on the metabolic profiles of individuals with energy abnormalities are still unclear. In the study, we investigated the effect of p-synephrine on energy homeostasis and metabolic profiles using a high fat diet (HFD)-induced mouse model. We found that p-synephrine inhibited the gain in body weight, liver weight and white adipose tissues weight induced by HFD. p-Synephrine supplementation also reduced levels of serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) but not to a statistically significant degree. Histological analysis showed that HFD induced excessive lipid accumulation and glycogen loss in the liver and adipocyte enlargement in perirenal fat tissue, while p-synephrine supplementation reversed the changes induced by HFD. Moreover, HFD feeding significantly increased mRNA expression levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and reduced the mRNA expression level of interleukin-10 (IL-10) compared to the control group, while p-synephrine supplementation significantly reversed these HFD-induced changes. Liver and serum metabolomic analysis showed that p-synephrine supplementation significantly altered small molecule metabolites in liver and serum in HFD mice and that the changes were closely associated with improvement of energy homeostasis. Notably, amino acid metabolism pathways, both in liver and serum samples, were significantly enriched. Our study suggests that p-synephrine improves energy homeostasis probably by regulating amino acid metabolism in HFD mice, which provides a novel insight into the action mechanism of p-synephrine modulating energy homeostasis.

Combined Anti-Adipogenic Effects of Hispidulin and p-Synephrine on 3T3-L1 Adipocytes

Hispidulin is abundant in Arrabidaea chica, Crossostephium chinense, and Grindelia argentina, among others. p-Synephrine is the main phytochemical constituent of Citrus aurantium. It has been used in combination with various other phytochemicals to determine synergistic effects in studies involving human participants. However, there have been no reports comparing the anti-adipogenic effects of the combination of hispidulin and p-synephrine. The current study explores the anti-adipogenic effects of hispidulin alone and in combination with p-synephrine in a murine preadipocyte cell line, 3T3-L1. Co-treatment resulted in a greater inhibition of the formation of red-labeled lipid droplets than the hispidulin or p-synephrine-alone treatments. Co-treatment with hispidulin and p-synephrine also significantly inhibited adipogenic marker proteins, including Akt, mitogen-activated protein kinases, peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein alpha, glucocorticoid receptor, and CCAAT/enhancer-binding protein β. Although further studies are required to assess the effects of each drug on pharmacokinetic parameters, a combination treatment with hispidulin and p-synephrine may be a potential alternative strategy for developing novel anti-obesity drugs.

Synephrine and caffeine combination promotes cytotoxicity, DNA damage and transcriptional modulation of apoptosis-related genes in human HepG2 cells

The abusive consumption of thermogenic supplements occurs worldwide and deserves special attention due to their use to stimulate weight loss and prevent obesity. Thermogenic formulations usually contain Synephrine (SN) and Caffeine (CAF), stimulating compounds extracted from natural sources, but no genetic toxicology studies have predicted this hazardous combination potential. This study examined the toxicogenomic responses induced by SN and CAF, either alone or in combination, in the human hepatic cell line HepG2 in vitro. SN (0.03-30 μM) and CAF (0.6-600 μM) alone did neither decrease cell viability nor induce DNA damage, as assessed using the MTT and comet assays, respectively. SN (3 μM) and CAF (30-600 μM) were combined at concentrations similar to those found in commercial dietary supplements. SN/CAF at 3:90 and 3:600 μM ratios significantly decreased cell viability and increased DNA damage levels in HepG2 cells. CAF (600 μM) and the SN/CAF association at 3:60, 3:90, and 3:600 μM ratios promoted cell death by apoptosis, as demonstrated by flow cytometry. Similar results were observed in gene expression (RT-qPCR): SN/CAF up-regulated the expression of apoptosis- (BCL-2 and CASP9) and DNA repair-related (XPC) genes. SN/CAF at 3:90 μM also downregulated the expression of cell cycle control (CDKN1A) genes. In conclusion, the SN/CAF combination reduces cell viability by inducing apoptosis, damages DNA, and modulates the transcriptional expression of apoptosis-, cell cycle-, and DNA repair-related genes in human hepatic (HepG2) cells in vitro. These effects can be worrisome to consumers of thermogenic supplements.

Deciphering the synergistic network regulation of active components from SiNiSan against irritable bowel syndrome via a comprehensive strategy: Combined effects of synephrine, paeoniflorin and naringin

BACKGROUND

SiNiSan (SNS) is an ancient Chinese herbal prescription, and the current clinical treatment of irritable bowel syndrome (IBS) is effective. In the previous study of the research team, the multi-functional co-synergism of SNS against IBS was presented. Some potential drug targets and candidate ligands were predicted.

PURPOSE

This study attempts to explore the crucial ingredient combinations from SNS formula and reveal their synergistic mechanism for IBS therapy.

MATERIALS AND METHODS

In present study, a comprehensive strategy was performed to reveal IBS related pathways and biological modules, and explore synergistic effects of the ingredients, including ADME (absorption, distribution, metabolism, excretion) screening, Text mining, Venn analysis, Gene ontology (GO) analysis, Pathway cluster analysis, Molecular docking, Network construction and Experimental verification in visceral hypersensitivity (VHS) rats.

RESULTS

Three compressed IBS signal pathways were derived from ClueGO KEGG analysis of 63 IBS genes, including Neuroactive ligand-receptor interaction, Inflammatory mediator regulation of TRP (transient receptor potential) channels and Serotonergic synapse. A multi-module network, composed of four IBS therapeutic modules (psychological, inflammation, neuroendocrine and cross-talk modules), was revealed by Target-Pathway network. Nine kernel targets were considered closely associated with the IBS pathways, including ADRA2A, HTR2A, F2RL1, F2RL3, TRPV1, PKC, PKA, IL-1Β and NGF. In silico analysis revealed that three crucial ingredients (synephrine, paeoniflorin and naringin) were assumed to coordinate the network of those IBS therapeutic modules by acting on these kernel targets in the important pathways. In vivo experimental results showed that the crucial ingredient combinations synergistically affected the expressions of the kernel biological molecules, and improved the minimum capacity threshold of AWR in VHS rats.

CONCLUSION

The study proposes the important IBS associated pathways and the network regulation mechanisms of the crucial ingredients. It reveals the multi-target synergistic effect of the crucial ingredient combinations for the novel therapy on IBS.

Effects of p-Synephrine during Exercise: A Brief Narrative Review

The p-synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements have been marketed without proper knowledge of their true effectiveness to enhance fat utilization, especially when combined with exercise. However, the effects of p-synephrine on fat oxidation during exercise have been investigated in the last few years. The aim of the current discussion is to summarize the evidence on the effects of p-synephrine intake on fat oxidation and performance during exercise. Previous investigations have demonstrated that the acute intake of p-synephrine does not modify running sprint performance, jumping capacity, or aerobic capacity. However, the acute intake of p-synephrine, in a dose of 2-3 mg/kg of body mass, has been effective to enhance the rate of fat oxidation during incremental and continuous exercise. This effect has been observed in a range of exercise workloads between 30% and 80% of peak oxygen uptake (VO_2peak). The p-synephrine has the ability to increase the maximal rate of fat oxidation during exercise of increasing intensity without affecting the workload at which maximal fat oxidation is obtained (Fatmax). The effect of p-synephrine on fat oxidation is normally accompanied by a concomitant reduction of carbohydrate utilization during exercise, without modifying the energy expended during exercise. The shifting in substrate oxidation is obtained without any effect on heart rate during exercise and the prevalence of adverse effects is negligible. Thus, the acute use of p-synephrine, or p-synephrine-containing products, might offer some benefits for those individuals seeking higher fat utilization during exercise at low to moderate intensities. However, more research is still necessary to determine if the effect of p-synephrine on fat oxidation during exercise is maintained with chronic ingestion, in order to ascertain the utility of this substance in conjunction with exercise programs to produce an effective body fat/weight loss reduction.

Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p-Synephrine

Citrus aurantium L. (bitter orange) extracts that contain p-synephrine as the primary protoalkaloid are widely used for weight loss/weight management, sports performance, appetite control, energy, and mental focus and cognition. Questions have been raised about the safety of p-synephrine because it has some structural similarity to ephedrine. This review focuses on current human, animal, in vitro, and mechanistic studies that address the safety, efficacy, and mechanisms of action of bitter orange extracts and p-synephrine. Numerous studies have been conducted with respect to p-synephrine and bitter orange extract because ephedra and ephedrine were banned from use in dietary supplements in 2004. Approximately 30 human studies indicate that p-synephrine and bitter orange extracts do not result in cardiovascular effects and do not act as stimulants at commonly used doses. Mechanistic studies suggest that p-synephrine exerts its effects through multiple actions, which are discussed. Because p-synephrine exhibits greater adrenergic receptor binding in rodents than humans, data from animals cannot be directly extrapolated to humans. This review, as well as several other assessments published in recent years, has concluded that bitter orange extract and p-synephrine are safe for use in dietary supplements and foods at the commonly used doses. Copyright © 2017 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd.

Effects of acute ingestion of a pre-workout dietary supplement with and without p-synephrine on resting energy expenditure, cognitive function and exercise performance

BACKGROUND

The purpose of this study was to examine the effects of acute ingestion of a pre-workout dietary supplement (PWS) with and without p-synephrine (S) on perceptions of readiness to perform, cognitive function, exercise performance, and markers of safety.

METHODS

In a randomized, double-blind, and counterbalanced manner; 25 healthy and recreationally active male and female participants ingested a flavored maltodextrin placebo (PLA), a PWS containing beta-alanine (3 g), creatine nitrate as a salt (2 g), arginine alpha-ketoglutarate (2 g), N-Acetyl-L-Tyrosine (300 mg), caffeine (284 mg), Mucuna pruiriens extract standardized for 15% L-Dopa (15 mg), Vitamin C as Ascorbic Acid (500 mg), niacin (60 mg), folate as folic acid (50 mg), and Vitamin B12 as Methylcobalamin (70 mg) with 2 g of maltodextrin and flavoring; or, the PWS with Citrus aurantium (PWS + S) extract standardized for 30% p-synephrine (20 mg). Participants had heart rate (HR), blood pressure, resting energy expenditure (REE), 12-lead electrocardiograms (ECG), perceptions about readiness to perform, cognitive function (Stroop Color-Word test), bench and leg press performance (2 sets of 10 repetitions at 70% of 1RM and 1 set to failure), and Wingate anaerobic capacity (WAC) sprint performance determined as well as donated blood samples prior to and/or following exercise/supplementation. Data were analyzed by MANOVA with repeated measures as well as mean changes from baseline with 95% confidence intervals (CI).

RESULTS

No clinically significant differences were observed among treatments in HR, blood pressure, ECG, or general clinical blood panels. There was evidence that PWS and PWS + S ingestion promoted greater changes in REE responses. Participants reported higher perception of optimism about performance and vigor and energy with PWS and PWS + S ingestion and there was evidence that PWS and PWS + S improved changes in cognitive function scores from baseline to a greater degree than PLA after 1 or 2 h. However, the scores in the PWS + S treatment did not exceed PLA or PWS responses at any data point. No statistically significant differences were observed among treatments in total bench press lifting volume, leg press lifting volume or WAC sprint performance.

CONCLUSIONS

Within the confines of this study, ingestion of PWS and/or PWS + S prior to exercise appears to be well-tolerated when consumed by young, healthy individuals. The primary effects appear to be to increase REE responses and improve perceptions about readiness to perform and cognitive function with limited to no effects on muscular endurance and WAC. The addition of 20 mg of p-synephrine to the PWS provided limited to no additive benefits.

TRIAL REGISTRATION

This trial (NCT02952014) was retrospectively registered on September 13th 2016.

A Review of Natural Stimulant and Non-stimulant Thermogenic Agents

Obesity and overweight are major health issues. Exercise and calorie intake control are recognized as the primary mechanisms for addressing excess body weight. Naturally occurring thermogenic plant constituents offer adjunct means for assisting in weight management. The controlling mechanisms for thermogenesis offer many intervention points. Thermogenic agents can act through stimulation of the central nervous system with associated adverse cardiovascular effects and through metabolic mechanisms that are non-stimulatory or a combination thereof. Examples of stimulatory thermogenic agents that will be discussed include ephedrine and caffeine. Examples of non-stimulatory thermogenic agents include p-synephrine (bitter orange extract), capsaicin, forskolin (Coleus root extract), and chlorogenic acid (green coffee bean extract). Green tea is an example of a thermogenic with the potential to produce mild but clinically insignificant undesirable stimulatory effects. The use of the aforementioned thermogenic agents in combination with other extracts such as those derived from Salacia reticulata, Sesamum indicum, Lagerstroemia speciosa, Cissus quadrangularis, and Moringa olifera, as well as the use of the carotenoids as lutein and fucoxanthin, and flavonoids as naringin and hesperidin can further facilitate energy metabolism and weight management as well as sports performance without adverse side effects. © 2016 The Authors Phytotherapy Research published by John Wiley & Sons Ltd.

The effects of supplementation with P-Synephrine alone and in combination with caffeine on resistance exercise performance

BACKGROUND

Little is known concerning the potential ergogenic effects of p-synephrine supplementation. Therefore, the purpose of the present study was to examine the effects of supplementation with p-synephrine alone and in combination with caffeine on free-weight resistance exercise performance.

METHODS

Twelve healthy, college-aged men performed a control (CT) resistance exercise protocol consisting of 6 sets of squats for up to 10 repetitions per set using 80% of their one repetition-maximum (1RM) with 2 min of rest in between sets. Each subject was randomly assigned (in double-blind, balanced manner) to a treatment sequence consisting of use of 3 supplements: p-synephrine (S; 100 mg), p-synephrine + caffeine (SCF; 100 mg of p-synephrine plus 100 mg of caffeine), or a placebo (P). For each supplement treatment (separated by 1 week), subjects consumed the supplement for 3 days prior to each protocol and the morning of each protocol, and subsequently did not consume any supplements for 3 days following (i.e. wash-out period). On each protocol day, subjects reported to the lab at a standard time, consumed a supplement, sat quietly for 45 min, performed the resistance exercise protocol, and sat quietly for 30 min post exercise. Performance (repetition number, force, velocity and power), blood lactate, and ratings of perceived exertion (RPE) data were collected during each protocol.

RESULTS

Supplements SCF and S produced a significantly (P < 0.05) greater number of repetitions performed than CT (by 11.0 ± 8.0%) and P (by 6.0 ± 7.0%) and a 10.6 ± 12.0% greater increase in volume load per protocol than CT and P. Most of the differences were seen during the last 3 sets. Mean power and velocity for all 6 sets were significantly higher in SCF compared to CT and P by ~6.2 ± 8.0%. No supplement effects were observed in RPE or blood lactate, and no adverse side effects were observed or reported.

CONCLUSIONS

S and SCF augmented resistance exercise performance (total repetitions, volume load) without increasing blood lactate or RPE. The addition of caffeine in SCF increased mean power and velocity of squat performance. These results indicate supplementation with S and SCF can enhance local muscle endurance during resistance exercise.

The action of p-synephrine on hepatic carbohydrate metabolism and respiration occurs via both Ca(2+)-mobilization and cAMP production

Citrus aurantium extracts, which contain large amounts of p-synephrine, are widely used for weight loss purposes and as appetite suppressants. In the liver, C. aurantium (bitter orange) extracts affect hemodynamics, carbohydrate metabolism, and oxygen uptake. The purpose of the present work was to quantify the action of p-synephrine and also to obtain indications about its mechanism of action, a task that would be difficult to accomplish with C. aurantium extracts due to their rather complex composition. The experimental system was the isolated perfused rat liver. p-Synephrine significantly stimulated glycogenolysis, glycolysis, gluconeogenesis, and oxygen uptake. The compound also increased the portal perfusion pressure and the redox state of the cytosolic NAD(+)/NADH couple. A Ca(2+)-dependency for both the hemodynamic and the metabolic effects of p-synephrine was found. p-Synephrine stimulated both cAMP overflow and the initial Ca(2+) release from the cellular stores previously labeled with (45)Ca(2+). The metabolic and hemodynamic actions of p-synephrine were strongly inhibited by α-adrenergic antagonists and moderately affected by β-adrenergic antagonists. The results allow to conclude that p-synephrine presents important metabolic and hemodynamic effects in the liver. These effects can be considered as both catabolic (glycogenolysis) and anabolic (gluconeogenesis), they are mediated by both α- and β-adrenergic signaling, require the simultaneous participation of both Ca(2+) and cAMP, and could be contributing to the overall stimulation of metabolism that usually occurs during weight loss periods.

A review of the human clinical studies involving Citrus aurantium (bitter orange) extract and its primary protoalkaloid p-synephrine

This review summarizes the published as well as unpublished human studies involving Citrus aurantium (bitter orange) extract and its primary protoalkaloid p-synephrine, providing information and an assessment of the safety and efficacy of these widely used products. The results of over 20 studies involving a total of approximately 360 subjects that consumed p-synephrine alone or in combination with other ingredients are reviewed and critiqued. Over 50 % of the subjects involved in these studies were overweight/obese, and approximately two-thirds of these overweight/obese subjects consumed caffeine (132-528 mg/day) in conjunction with p-synephrine (10-53 mg/day). Bitter orange/p-synephrine containing products were consumed for up to 12 weeks. Approximately 44 % of the subjects consumed a bitter orange/p-synephrine only product, while the remainder consumed a complex product that contained multiple ingredients in addition to p-synephrine. In general, bitter orange extract alone (p-synephrine) or in combination with other herbal ingredients did not produce significant adverse events as an increase in heart rate or blood pressure, or alter electrocardiographic data, serum chemistry, blood cell counts or urinalysis. p-Synephrine alone as well as in combination products were shown to increase resting metabolic rate and energy expenditure, and modest increases in weight loss were observed with bitter orange extract/p-synephrine-containing products when given for six to 12 weeks. Longer term studies are needed to further assess the efficacy of these products and affirm their safety under these conditions.

Effects of Citrus aurantium (bitter orange) fruit extracts and p-synephrine on metabolic fluxes in the rat liver

The fruit extracts of Citrus aurantium (bitter orange) are traditionally used as weight-loss products and as appetite supressants. An important fruit component is p-synephrine, which is structurally similar to the adrenergic agents. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of the C. aurantium extract on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways, including oxygen uptake and perfusion pressure. The C. aurantium extract and p-synephrine increased glycogenolysis, glycolysis, oxygen uptake and perfusion pressure. These changes were partly sensitive to α- and β-adrenergic antagonists. p-Synephrine (200 μM) produced an increase in glucose output that was only 15% smaller than the increment caused by the extract containing 196 μM p-synephrine. At low concentrations the C. aurantium extract tended to increase gluconeogenesis, but at high concentrations it was inhibitory, opposite to what happened with p-synephrine. The action of the C. aurantium extract on liver metabolism is similar to the well known actions of adrenergic agents and can be partly attributed to its content in p-synephrine. Many of these actions are catabolic and compatible with the weight-loss effects usually attributed to C. aurantium.

p-Synephrine stimulates glucose consumption via AMPK in L6 skeletal muscle cells

Interest in p-synephrine, the primary protoalkaloid in the extract of bitter orange and other citrus species, has increased due to its various pharmacological effects and related adverse effects. The lipolytic activity of p-synephrine has been repeatedly revealed by in vitro and in vivo studies and p-synephrine is currently marketed as a dietary supplement for weight loss. The present study investigated the effect of p-synephrine on glucose consumption and its action mechanism in L6 skeletal muscle cells. Treatment of L6 skeletal muscle cells with p-synephrine (0-100μM) did not affect cell viability and increased basal glucose consumption up to 50% over the control in a dose-dependent manner. The basal- or insulin-stimulated lactic acid production as well as glucose consumption was significantly increased by the addition of p-synephrine. p-Synephrine stimulated the phosphorylation of AMPK but not of Akt. p-Synephrine-induced glucose consumption was sensitive to the inhibition of AMPK but not to the inhibition of PI3 kinase. p-Synephrine also stimulated the translocation of Glut4 from the cytoplasm to the plasma membrane; this stimulation was suppressed by the inhibition of AMPK, but not of PI3 kinase. Taken together, p-synephrine can stimulate glucose consumption (Glut4-dependent glucose uptake) by stimulating AMPK activity, regardless of insulin-stimulated PI3 kinase-Akt activity in L6 skeletal muscle cells.

A review of the receptor-binding properties of p-synephrine as related to its pharmacological effects

Bitter orange (Citrus aurantium) extract and its primary protoalkaloid p-synephrine are used widely in weight loss/weight management and sports performance products. Because of structural similarities, the pharmacological effects of p-synephrine are widely assumed to be similar to those of ephedrine, m-synephrine (phenylephrine), and endogenous amine neurotransmitters as norepinephrine and epinephrine. However, small structural changes result in the receptor binding characteristics of these amines that are markedly different, providing a plausible explanation for the paucity of adverse effects associated with the wide-spread consumption of p-synephrine in the form of dietary supplements as well as in various Citrus foods and juices. This paper summarizes the adrenoreceptor binding characteristics of p-synephrine relative to m-synephrine, norepinephrine, and other amines as related to the observed pharmacological effects.

Effects of p-synephrine alone and in combination with selected bioflavonoids on resting metabolism, blood pressure, heart rate and self-reported mood changes

Bitter orange (Citrus aurantium) extract is widely used in dietary supplements for weight management and sports performance. Its primary protoalkaloid is p-synephrine. Most studies involving bitter orange extract and p-synephrine have used products with multiple ingredients. The current study assessed the thermogenic effects of p-synephrine alone and in conjunction with the flavonoids naringin and hesperidin in a double-blinded, randomized, placebo-controlled protocol with 10 subjects per treatment group. Resting metabolic rates (RMR), blood pressure, heart rates and a self-reported rating scale were determined at baseline and 75 min after oral ingestion of the test products in V-8 juice. A decrease of 30 kcal occurred in the placebo control relative to baseline. The group receiving p-synephrine (50 mg) alone exhibited a 65 kcal increase in RMR as compared to the placebo group. The consumption of 600 mg naringin with 50 mg p-synephrine resulted in a 129 kcal increase in RMR relative to the placebo group. In the group receiving 100 mg hesperidin in addition to the 50 mg p-synephrine plus 600 mg naringin, the RMR increased by 183 kcal, an increase that was statistically significant with respect to the placebo control (p<0.02). However, consuming 1000 mg hesperidin with 50 mg p-synephrine plus 600 mg naringin resulted in a RMR that was only 79 kcal greater than the placebo group. None of the treatment groups exhibited changes in heart rate or blood pressure relative to the control group, nor there were no differences in self-reported ratings of 10 symptoms between the treatment groups and the control group. This unusual finding of a thermogenic combination of ingredients that elevated metabolic rates without corresponding elevations in blood pressure and heart-rates warrants longer term studies to assess its value as a weight control agent.

Effect of acute administration of an herbal preparation on blood pressure and heart rate in humans

Confusion and controversy exist regarding the cardiovascular effects of dietary supplements containing caffeine and Citrus aurantium (bitter orange) extract. The primary protoalkaloidal ingredient in bitter orange extract is p-synephrine which has some structural similarities to ephedrine and nor-epinephrine, but exhibits markedly different pharmacokinetic and receptor binding properties. The goal of this study was to investigate the cardiovascular effects of a product containing caffeine, bitter orange extract (p-synephrine) and green tea extract in mildly overweight individuals. Fourteen female and nine male subjects (age 24.7 ±7.4 yrs, BMI: 26.6 ±3.8) volunteered in this randomized, placebo-controlled, crossover, double-blind designed study. On day one, subjects entered the laboratory following an overnight fast. Heart rate and blood pressure were recorded at 60 min. Expired air was analyzed for the next 10 min of the session. At each of three meals, subjects ingested one capsule that was either a non-caloric placebo or a dietary supplement that contained 13 mg p-synephrine and 176 mg caffeine. On the following day, the subjects returned and repeated the protocol for data collection beginning 60 min after consuming one capsule of the placebo or the dietary supplement. No effects of the dietary supplement on heart rate, systolic and diastolic blood pressure or mean arterial pressure were observed. No between or within group differences were observed when data were analyzed for gender and caffeine usage. A small but significant decrease in resting respiratory exchange ratio was observed for the low caffeine user group in response to the product containing caffeine and p-synephrine. The results of this study indicate that ingestion of a product containing bitter orange extract, caffeine and green tea extract does not lead to increased cardiovascular stress and that fat oxidation may increase in certain populations.

Effects of synephrine and beta-phenethylamine on human alpha-adrenoceptor subtypes

Synephrine and beta-phenethylamine, two naturally occurring compounds, are structurally related to ephedrine. In this study, the effects of synephrine and beta-phenethylamine on alpha-adrenergic receptor (alpha-AR) subtypes are investigated in human embryonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-norephedrine. The rank order of binding affinities was found to be the same for the subtypes tested (alpha(1A)-, alpha(2A)-, and alpha(2C)-AR) viz, 1R,2S-norephedrine > beta-phenethylamine > synephrine. Functional studies on the alpha(1A)-AR subtype showed that synephrine was a partial agonist giving a maximal response at 100 microM that was equal to 55.3 % of the L-phenylephrine maximum. In contrast, neither 1R,2S-norephedrine nor beta-phenethylamine exhibited agonist activity at the highest concentration tested (300 microM). beta-Phenethylamine was more potent as an antagonist than 1R,2S-norephedrine and synephrine on the alpha(1A)-AR subtype. Functional studies on the alpha(2A)- and alpha(2C)-AR subtypes indicated that synephrine and beta-phenethylamine did not act as agonists. Similar to 1R,2S-norephedrine, both of these analogs reversed the effect of medetomidine against forskolin-induced cAMP elevations at 300 microM, and the rank order of antagonist potency was: 1R,2S-norephedrine = beta-phenethylamine > synephrine; and beta-phenethylamine > 1R,2S-norephedrine > synephrine, respectively. These differences suggest that the presence of a 4-hydroxy group, as in synephrine, reduced the potency in these subtypes. In conclusion, at the alpha(1A)-AR, synephrine acted as a partial agonist, while beta-phenethylamine did not exhibit any direct agonist activity. Both, synephrine and beta-phenethylamine, may act as antagonists of pre-synaptic alpha(2A/2C)-ARs present in nerve terminals.

Therapeutic and adverse effects of a non-steroidal glucocorticoid receptor ligand in a mouse model of multiple sclerosis

Background

Dissociating glucocorticoid receptor (GR) ligands hold great promise for treating inflammatory disorders since it is assumed that they exert beneficial activities mediated by transrepression but avoid adverse effects of GR action requiring transactivation. Here we challenged this paradigm by investigating 2-(4-acetoxyphenyl)-2-chloro-N-methyl-ethylammonium chloride (CpdA), a dissociating non-steroidal GR ligand, in the context of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS).

Methodology/Principal Findings

CpdA inhibited pro-inflammatory mediators in myelin-specific T cells and fibroblasts in a GR-dependent manner while gene activation was abolished. However, it also induced massive apoptosis in various cell types even in the absence of the GR by engaging a Bcl-2- and caspase-dependent pathway. ¹H NMR spectroscopy corroborated these findings by revealing that CpdA dissolved in buffered solutions rapidly decomposes into aziridine intermediates known to act as alkylating pro-apoptotic agents. Importantly, the dichotomy of CpdA action also became evident in vivo. Administration of high-dose CpdA to mice was lethal while treatment of EAE with low to intermediate amounts of CpdA dissolved in water significantly ameliorated the disease. The beneficial effect of CpdA required expression of the GR in T cells and was achieved by down regulating LFA-1 and CD44 on peripheral Th cells and by repressing IL-17 production.

Conclusions/Significance

CpdA has significant therapeutic potential although adverse effects severely compromise its application in vivo. Hence, non-steroidal GR ligands require careful analysis prior to their translation into new therapeutic concepts.

Effect of constituents from Fructus Aurantii Immaturus and Radix Paeoniae Alba on gastrointestinal movement

Fructus Aurantii Immaturus and Radix Paeoniae Alba Powder (FPP) is a popular Chinese herbal prescription. The combination of Fructus Aurantii Immaturus and Radix Paeoniae Alba has been used to treat gastrointestinal disorders for hundreds of years. To our interest, this combination shows a bilateral effect on gastrointestinal peristalsis. Our present study was focused on the bilateral role of this combination on the gastrointestinal tract. The effective constituents and mechanisms were explored. Six monomer constituents from Radix Paeoniae Alba and Fructus Aurantii Immaturus were screened by intestinal transit assay. The bilateral roles of three effective constituents were authenticated by gastric emptying assay, and the combination of three constituents showed a bilateral effect. Then, the mediating receptors and the role of NO and NF- kappaB p65 were examined to determine the mechanism involved. The overall results suggest that the major effective constituents of this combination are synephrine, hesperidin and paeoniflorin. Synephrine inhibits the gastrointestinal movement, while hesperidin stimulates it. Paeoniflorin shows different effects on intestinal and gastric activity. The effect of synephrine relies on the alpha-adrenergic receptor, and the effect of hesperidin is mediated via the H1 histamine receptor. The regulation of hesperidin and synephrine on NF- kappaB p65 translocation and NO production through the alpha-receptor and the H1 receptor, respectively, is involved in the bilateral effect of the Fructus Aurantii Immaturus-Radix Paeoniae Alba combination.

Chemical and biological comparisons on Evodia with two related species of different locations and conditions

Evodia rutaecarpa (ER) and Tetradium glabrifolium (TG) are closely related species collected from different locations, with processed versus unprocessed and fresh versus 1-year-old samples. The purpose of this study is to determine the variability of their bioactive constituents; evodiamine, dehydroevodiamine, rutaecarpine and synephrine--as well as their relaxing effects on an isolated rat aortas and uterus using the extracts of the test specimens. The vasorelaxation was greater in ER from Taiwan than from China in spite of lower levels of the relaxing alkaloids evodiamine, dehydroevodiamine and rutaecarpine. On the other hand, the uterine relaxation of ER from China was better than the one from Taiwan, even though constricting synephrine was only contained in Chinese ER. After processing, the relaxation of ER from China in the uterus was increased while the vasorelaxation remained unchanged. Conversely, TG from Wu-ling contained more relaxing alkaloids than that from Lee Mountain. However, the relaxation in both the uterus and the aorta was less in TG from Wu-ling. After 1 year of storage, the vasorelaxation of TG from Lee Mountain was not changed. Taken together, a significant finding in the present study is the lack of correction between chemical composition and relaxing activities. This strongly supports our assumption that biological function evaluations, instead of chemical standardization, is the more adequate way of showing meaningful consistency of natural preparations.

Anti-inflammatory effects and mechanisms of the ethanol extract of Evodia rutaecarpa and its bioactive components on neutrophils and microglial cells

Evodia rutaecarpa is commonly used as an anti-inflammatory drug in traditional Chinese medicine. We previously identified four bioactive compounds (dehydroevodiamine (I), evodiamine (II), rutaecarpine (III), and synephrine (IV)) from the ethanol extract of E. rutaecarpa, but their effects and mechanism(s) of action remain unclear. To study the anti-inflammatory potential and the possible underlying mechanism(s), their effects on phorbol-12-myristate-13-acetate (PMA)- and N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced reactive oxygen species production in neutrophils was studied, as well as lipopolysaccharide (LPS)-induced nitric oxide (NO) production and inducible NO synthetase (iNOS) expression in microglial cells. The ethanol extract of E. rutaecarpa displayed potent antioxidative effects against both PMA- and fMLP-induced reactive oxygen species production in neutrophils (with IC50 values of around 2.7-3.3 microg/ml). Although less potent than the ethanol extract of E. rutaecarpa, compounds I-IV all concentration-dependently inhibited PMA- and fMLP-induced reactive oxygen species production, with compound IV consistently being the most potent agent among these active components. The antioxidative effects of the ethanol extract of E. rutaecarpa and these compounds were partially due to inhibition (10%-33%) of NADPH oxidase activity, a predominant reactive oxygen species-producing enzyme in neutrophils, and to a minor extent to their direct radical-scavenging properties. The ethanol extract of E. rutaecarpa also inhibited LPS-induced NO production (with an IC50 of around 0.8 microg/ml) and iNOS upregulation in microglial cells that was partially mimicked by compounds I, II, and III, but not compound IV. Our results suggest that the ethanol extract of E. rutaecarpa and its four bioactive components all exhibited anti-inflammatory activities which could be partially explained by their different potentials for inhibiting NADPH oxidase-dependent reactive oxygen species and/or iNOS-dependent NO production in activated inflammatory cells.

Citrus aurantium and synephrine alkaloids in the treatment of overweight and obesity: an update

Obesity is a major health problem facing the developed and developing world. Efforts by individuals, health professionals, educators, and policy makers to combat the escalating trend of growing obesity prevalence have been multifaceted and mixed in outcome. Various dietary supplements have been marketed to reduce obesity. These products have been suggested to accomplish this by decreasing energy intake and energy absorption, and/or increasing metabolic rate. Ephedra, one such supplement, was banned from sale in the US market because of concerns about adverse events. Another substance, Citrus aurantium, which contains several compounds including synephrine alkaloids, has been suggested as a safe alternative. This review examines the evidence for safety and efficacy of C. aurantium and synephrine alkaloids as examined in animal studies, clinical weight loss trials, acute physiologic studies and case reports. Although at least three reviews of C. aurantium have been published, our review expands upon these by: (i) distinguishing and evaluating the efficacy of C. aurantium and related compounds; (ii) including results from previously unreviewed research; (iii) incorporating recent case reports that serve to highlight, in an anecdotal way, potential adverse events related to the use of C. aurantium and related compounds; and (iv) offering recommendations to guide the design of future trials to evaluate the safety and efficacy of C. aurantium. While some evidence is promising, we conclude that larger and more rigorous clinical trials are necessary to draw adequate conclusions regarding the safety and efficacy of C. aurantium and synephrine alkaloids for promoting weight loss.

Seville (sour) orange juice: synephrine content and cardiovascular effects in normotensive adults

The Seville orange extract Citrus aurantium contains m-synephrine (phenylephrine) and octopamine; it causes cardiac disturbances in animals and is used by humans for weight loss. Juice from the orange (Seville orange juice [SOJ]) is used to "knock out" intestinal cytochrome P450 (CYP) 3A4 in bioavailability studies. The purpose of this study was to determine synephrine and octopamine concentrations in SOJ and SOJ's cardiovascular effects in normotensive humans. Subjects consumed 8 ounces of SOJ and water in crossover fashion followed by a repeat ingestion 8 hours later. Hemodynamic (heart rate; systolic, diastolic, and mean arterial pressure) measurements followed. Synephrine and octopamine were determined by high-performance liquid chromatography. Hemodynamics did not differ significantly between water and SOJ groups. Mean synephrine concentration of SOJ samples was 56.9 +/- 0.52 microg/ml; octopamine was not detected. SOJ ingestion by normotensive subjects is expected to be safe. Individuals with severe hypertension, tachyarrhythmias, and narrow-angle glaucoma and monoamine oxidase inhibitor recipients should avoid SOJ consumption. Persons taking decongestant-containing cold preparations should also refrain from SOJ intake.

Characterization of antidepressant-like effects of p-synephrine stereoisomers

We previously reported that p-synephrine has antidepressant-like activity in the murine models of forced swimming and tail suspension. In the present study, we characterized antidepressant-like effects of p-synephrine stereoisomers in both in vivo and in vitro systems. In the tail suspension test, S-(+)-p-synephrine (3 mg/kg, p.o.) reduced the duration of immobility, while R-(-)-p-synephrine (0.3-3 mg/kg, p.o.) had no effect. S-(+)-p-synephrine (0.3, 1 and 3 mg/kg, p.o.) and R-(-)-p-synephrine (1 mg/ kg and 3 mg/kg, p.o.) significantly reversed the reserpine (2.5 mg/kg, i.p.)-induced hypothermia. S-(+)-p-synephrine was more effective than R-(-)-p-synephrine in inhibition of both [3H]noradrenaline uptake in rat cerebral cortical slices (maximal inhibition 85.7 +/- 7.8% vs. 59.8 +/- 4.3%; EC50 5.8 +/- 0.7 microM vs. 13.5 +/- 1.2 microM) and [3H]nisoxetine binding (Ki 4.5 +/- 0.5 microM vs. 8.2 +/- 0.7 microM). In contrast, R-(-)-p-synephrine was more effective than S-(+)-p-synephrine in stimulation of [3H]noradrenaline release from rat cerebral cortical slices (maximal stimulation 23.9 +/- 1.8% vs. 20.1 +/- 1.7%; EC50 8.2 +/- 0.6 microM vs. EC50 12.3 +/- 0.9 microM). The stimulatory effect of R-(-)-p-synephrine on [3H]noradrenaline release was inhibited by nisoxetine (100 nM), but tetrodotoxin (1 microM) and elimination of extracellular calcium had no effect. It is suggested that S-(+)-p-synephrine has more effective antidepressant-like activity than R-(-)-p-synephrine.

Hemodynamic effects of synephrine treatment in portal hypertensive rats

Synephrine, a sympathomimetic alpha1-adrenoceptor agonist, has been shown to induce dose-dependent portal hypotensive effects after acute intravenous infusion. The present study was undertaken to investigate the hemodynamic effects of 8-day administration of synephrine in portal hypertensive rats. Portal hypertension was induced by either partial portal vein ligation (PVL) or bile duct ligation (BDL). Portal hypertensive rats were allocated into one of two groups: vehicle group (0.1 N HCl, 0.5 ml/12 h) or synephrine group (1 mg/kg per 12 h), with 7 rats in each group. Synephrine or vehicle was administered by gavage into PVL and BDL rats for 8 consecutive days. Systemic as well as splanchnic hemodynamic parameters were measured thereafter. Synephrine significantly ameliorated the hyperdynamic state in both PVL and BDL rats. The portal venous pressure in PVL and BDL rats (-13.5% and -10.1%, respectively), portal tributary blood flow (-19.5% and -20.4%) and cardiac index (-12.1% and -18.8%) were significantly reduced, while mean arterial pressure (10.4% and 23.4%) and systemic (26.3% and 51.0%) as well as portal territory (47.1% and 67.7%) vascular resistance were enhanced by treatment of synephrine as compared with vehicle treatment. Our results showed that eight-day administration of synephrine exerted beneficial hemodynamic effects in two models of portal hypertensive rats.

The effect of biogenic amines and their analogs on carbohydrate metabolism in the fat body of the cockroach Blaberus discoidalis

Several biogenic amines and their analogs were examined for stimulatory effects on glycogen phosphorylase activity and trehalose biosynthesis in fat body of the cockroach, Blaberus discoidalis. Octopamine and synephrine were the most potent activators of fat body phosphorylase; 10 muM octopamine being nearly as effective as the hypertrehalosemic hormone (HTH). Epinephrine, norepinephrine, and tyramine produced intermediate effects, whereas dopamine, 5-hydroxytryptamine, and melatonin had no effect. The fat body octopamine receptors appeared to be pharmacologically related to vertebrate alpha-adrenergic receptors and belonged to the Octopamine1 class receptor. In contrast to previous reports, synephrine also induced both phosphorylase activation and hypertrehalosemia as effectively as octopamine. Demethylchlordimeform, a formamidine insecticide structurally similar to octopamine, also strongly activated fat body phosphorylase, possibly by interaction with the octopamine receptor.

Selective inhibition of adenylyl cyclase by octopamine via a human cloned alpha 2A-adrenoceptor

1. In this study we have compared the abilities of the enantiomers of the structural isomers of the phenolamines, octopamine and synephrine, and the catecholamines, noradrenaline and adrenaline, to couple selectively a human cloned alpha 2A-adrenoceptor, stably expressed in a Chinese hamster ovary (CHO) cell line, to G-protein linked second messenger pathways mediating an increase and a decrease in cyclic AMP production. 2. The catecholamines couple the alpha 2A-adrenoceptor to both an increase and a decrease in the rate of cyclic AMP production. In the absence of pertussis toxin pretreatment both catecholamines tested showed a dose-dependent decrease with a maximum at 100 nM. After pertussis toxin pretreatment they both produced a dose-dependent increase in cyclic AMP production with a maximum at 10 microM. 3. The phenolamines, octopamine and synephrine were only able to couple the alpha 2A-adrenoceptor to a dose-dependent decrease in cyclic AMP production at concentrations up to 1 mM, with the synephrine isomers being more potent than the corresponding octopamine isomers. The meta-isomers of both phenolamines were more potent than the corresponding para-isomers and the (-)-enantiomers were more potent than the (+)-enantiomers. Thus, (-)-meta-synephrine [(-)-phenylephrine] was the most effective isomer tested with an observable decrease occurring between 100 nM and 1 microM. 4. The effects of octopamine and the catecholamines on the decrease in cyclic AMP production were additive at submaximal concentrations, whilst octopamine reduced the stimulant effect of submaximal concentrations of noradrenaline on cyclic AMP production after pertussis toxin pretreatment. 5. The time courses of the inhibitory effects of both meta-octopamine and noradrenaline were parallel and peaked after a 1 min exposure to the agonist. In contrast, the stimulant effects of noradrenaline after pertussis toxin pretreatment were of a much slower time course with a maximum effect occurring after a 5 min incubation period. 6. Since octopamine and synephrine occur naturally in, and are co-released with catecholamines from, mammalian tissues, the results of the present study suggest that the human cloned alpha 2A-adrenoceptor can be coupled selectively by different endogenous agonists to G-protein pathways mediating the regulation of adenylyl cyclase activity.

Antidepressant-like effects of p-synephrine in mouse models of immobility tests

We studied the effects of p-synephrine on the immobility behaviors and on the spontaneous motor activity in mice. p-Synephrine at oral doses from 1 to 10 mg/kg significantly decreased the duration of immobility in the tail suspension test and the forced swimming test in mice. At 30 mg/kg, the duration of immobility was returned to control values in both tests. Subcutaneous administration of prazosin hydrochloride (62.5 micrograms/kg), an alpha 1 adrenoceptor antagonist, blocked the p-synephrine (3 mg/kg)-induced decrease in immobility in the tail suspension test. p-Synephrine did not change the spontaneous motor activity at oral doses from 0.3 to 10 mg/kg. These results suggest that p-synephrine elicits an antidepressant-like activity in mouse models of immobility tests, through the stimulation of alpha 1 adrenoceptors.

Biogenic amines modulate synaptic transmission between identified giant interneurons and thoracic interneurons in the escape system of the cockroach

In the escape system of the cockroach, Periplaneta americana, a population of uniquely identifiable thoracic interneurons (type A or TIAs) receive information about wind via chemical synapses from a population of ventral giant interneurons (vGIs). The TIAs are involved in the integration of sensory information necessary for orienting the animal during escape. It is likely that there are times in an animal's life when it is advantageous to modify the effectiveness of synaptic transmission between the vGIs and the TIAs. Given the central position of the TIAs in the escape system, this would greatly alter associated motor outputs. We tested the ability of octopamine, serotonin, and dopamine to modulate synaptic transmission between vGIs and TIAs. Both octopamine and dopamine significantly increased the amplitude of vGI-evoked excitatory postsynaptic potentials (EPSPs) in TIAs at 10(-4)-10(-2) M, and 10(-3) M, respectively. On the other hand, serotonin significantly decreased the vGI-evoked EPSPs in TIAs at 10(-4)-10(-3) M. These results indicate that octopamine, serotonin, and dopamine are capable of modulating the efficacy of transmission of important neural connections within this circuit.

Activities of octopamine and synephrine stereoisomers on octopaminergic receptor subtypes in locust skeletal muscle

The activities of the (-) and (+)- forms of p-, m- and o-octopamine and p- and m-synephrine have been compared on the different subtypes of octopamine receptor present in the extensor-tibiae neuromuscular preparation from the locust hindleg. The rank order of potency of the (-)-forms on the OCTOPAMINE2A receptors was p-synephrine greater than p-octopamine greater than m-octopamine greater than o-octopamine greater than m-synephrine whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than m-octopamine. (+)-m-Synephrine and (+)-o-octopamine had no effect on this class of receptor when tested up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE2B receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine whilst the rank order of the (+)-forms was p-octopamine greater than p-synephrine greater than m-octopamine greater than o-octopamine. (+)-m-Synephrine again had no effect up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE1 receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine, whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than o-octopamine greater than m-synephrine greater than m-octopamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of octopamine and synephrine stereoisomers on alpha-adrenoceptors

1. The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on alpha 1-adrenoceptors from rat aorta and anococcygeus and alpha 2-adrenoceptors from rabbit saphenous vein were compared with those of noradrenaline (NA). 2. The rank order of potency of the (-)-forms on alpha 1-adrenoceptors from rat aorta and alpha 2-adrenoceptors was NA greater than m-octopamine = m-synephrine greater than p-octopamine = p-synephrine. The two m-compounds were 6 fold less active than NA on alpha 1-adrenoceptors from rat aorta and 150 fold less active on alpha 2-adrenoceptors. The two p- compounds were 1,000 fold less active than NA on both alpha 1-adrenoceptors from rat aorta and alpha 2-adrenoceptors. The rank order of potency of the (-)- forms on alpha 1-adrenoceptors from rat anococcygeus was NA = m-synephrine greater than m-octopamine greater than p-octopamine = p-synephrine. m-Octopamine was 4 fold less active than NA and (-)-m-synephrine. The two p- compounds were 30 fold less active than NA. 3. The rank order of potency of the (+)- forms was NA greater than m-octopamine greater than m-synephrine greater than p-octopamine greater than p-synephrine on both alpha 1- and alpha 2-adrenoceptors. The potency of each (+)- form was 1-2 orders of magnitude less than that of the (-) counterpart, the differences being greater for the stereoisomers of synephrine than for those of octopamine on both alpha 1- and alpha 2-adrenoceptors. 4. The yohimbine diastereoisomer antagonists, rauwolscine and corynanthine, were tested against (-)-NA and (-)-m-octopamine-induced contractions in both preparations. Based upon the known selectivities of these isomers for alpha-adrenoceptor subtypes, it is concluded that the rat aorta contains only alpha 1-adrenoceptors while the rabbit saphenous vein possesses predominantly alpha 2-adrenoceptors. 5. Ligand binding data for the octopamine and synephrine stereoisomers at alpha 1- and alpha 2-binding sites from rat cerebral cortex was also obtained. (-)-Forms were more active than (+)-forms. The rank order of affinity of the (-)-forms for both alpha 1- and alpha 2-binding sites was NA greater than m-octopamine = m-synephrine greater than p-synephrine greater than p-octopamine. The relative affinities of the members of the series against alpha 1-binding sites were very similar to their relative functional activities on rat aorta. However, the affinities of both m- and p-compounds relative to that of ( -)-NA were much greater at the x2-binding sites than were the relative activities in rabbit saphenous vein, possibly suggesting low intrinsic efficacy. Functional antagonist responses to NA by the (-)-octopamine and synephrines could not, however, be demonstrated on rat aorta or rabbit saphenous vein. 6. The activities of m-octopamine and m-synephrine were not significantly different from each other on either a,-adrenoceptors from rat aorta or x2-adrenoceptors; however, m-synephrine is more active than m-octopamine on a,-adrenoceptors from rat anococcygeus. Both m-octopamine and msynephrine can be considered to be naturally occurring x,-selective amines. However, if m- and poctopamine are co-released with NA in amounts proportional to their concentration, it is concluded that their activities on m,- and x2-adrenoceptors are too low to be physiologically significant.

Beta-adrenergic activities of octopamine and synephrine stereoisomers on guinea-pig atria and trachea

The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on beta 1- and beta 2-adrenoceptors in guinea-pig atria and trachea have been compared with that of noradrenaline. The rank order of potency of the (-)-forms on beta 1-adrenoceptors was noradrenaline greater than m-synephrine greater than m-octopamine = p-octopamine greater than p-synephrine. m-Synephrine was 100-fold, m- and p-octopamine about 6000-fold, and p-synephrine about 40,000-fold less active than noradrenaline. The (+)-forms were 1-2 orders of magnitude less active than their (-)-counterparts. The four (-)-compounds were more than four orders of magnitude less active than noradrenaline on beta 2-adrenoceptors, and the (+)-forms had no detectable activity in concentrations as high as 10(-4) M. If m- and p-octopamine are co-released with noradrenaline in amounts proportional to their concentration, their activities at these structures are too low to be physiologically significant.

A role for alternative pathway catecholamines in the regulation of steroidogenesis in cow luteal cells

Incubation of bovine luteal cells with the alternative pathway catecholamines octopamine, synephrine and deoxyadrenaline at concentrations of 10(-6) to 10(-3) M enhanced the production of progesterone (P less than 0.05). Tryamine did not alter basal progesterone production (P greater than 0.05). Addition of noradrenaline and adrenaline at concentrations of 10(-4) to 10(-7) M significantly elevated the production of progesterone (P less than 0.05). The steroidogenic response to noradrenaline and adrenaline was greater than that for octopamine, synephrine and deoxyadrenaline (P less than 0.05). Response to both primary (10(-6) M) and alternative (10(-4) M) pathway catecholamines was inhibited by propranolol (10(-5) M, P less than 0.05) but not phentolamine (10(-5) M, P greater than 0.05). These results demonstrate that octopamine, synephrine and deoxyadrenaline can affect steroidogenesis by bovine luteal cells, and their action is mediated by beta-adrenergic receptors.

Octopamine reduces potassium permeability of the glia that form the insect blood-brain barrier

Octopamine caused only a slight reduction in the potential across the perineurial glia of the cockroach, had no effect upon sodium-induced changes in potential, but did reduce potassium-induced changes (at 10(-7) M and above). The effect of 10(-7) M octopamine was accompanied by a rise in resistance, was mimicked by 10(-7) M synephrine and blocked by 10(-6) M phentolamine. Transperineurial potassium permeability was reduced by 10(-6) M octopamine. It is concluded that octopamine receptors mediate a reduction in potassium conductance of the basolateral membrane of these glia, and a reduction in the net potassium permeability of the barrier.

Pharmacological characterization of octopamine-sensitive adenylate cyclase in the flight muscle of Locusta migratoria L

Octopamine stimulates (20-30-fold) the adenylate cyclase activity in a broken cell preparation of locust flight muscle. This stimulation is mediated by one receptor with an apparent affinity of 3.3 X 10(-6) M. The hydroxyl group in the para position on phenylethanolamine was absolutely necessary to obtain an agonist whereas the meta hydroxyl group or the presence of a catechol almost suppressed the activity. Similar pharmacological profiles were obtained on other locust muscles, i.e. mandibular and extensor tibiae muscles. The affinities of a large series of agonists and antagonists for the octopamine receptor coupled with an adenylate cyclase were compared to those reported for octopamine 1, 2A and 2B receptors based on physiological studies in the locust extensor tibiae muscle. It appears that the octopamine receptor coupled with adenylate cyclase is likely to be identical with the octopamine 2A receptor mediating the increase in the amplitude of slow motoneuron twitch tension. The results of the pharmacological experiments are discussed, in particular concerning the possible relationship between the octopamine receptor and alpha 1- and alpha 2-adrenoceptors.

Receptors for 3H-octopamine in the adult firefly light organ

3H-Octopamine binds reversibly and with high affinity to sites on adult firefly light organ membranes. The binding is characterized by multiple affinities. Scatchard analysis supported a two site binding model with a tentative Kd value of about 1 nM for the high affinity component. The more abundant lower affinity site had a Kd value of about 60 nM. Guanyl nucleotides (Gpp(NH)p and GTP) greatly reduced the apparent number of octopamine binding sites. Competition studies with known octopaminergic agonists including the formamidine pesticides chlordimeform (CDM) and N-demethyl chlordimeform (DCDM) showed the following rank order of potencies in displacing octopamine: DCDM greater than octopamine = synephrine greater than naphazoline greater than clonidine greater than CDM. It was also observed that phentolamine was much more active than propranolol in antagonizing OA-binding. These relative activities are similar to the abilities of the same compounds to alter adenylate cyclase activity in light organ homogenates. Together with the effect of GTP on binding, these results suggest that the binding sites are functional octopamine receptors of the light organ.

Effect of intracerebroventricularly administered octopamines and synephrines on angiotensin II-induced water intake in rats

Recent studies from this laboratory showed that l-m-synephrine (phenylephrine), a metabolite of l-m-octapamine, inhibited the drinking response of rats to peripherally administered angiotensin II. The objective of this investigation was to determine whether the isomers of both octapamine and synephrine could inhibit angiotensin II-induced dipsogenesis in the rat. Of the isomers tested, only d,l-m-octopamine and l-m-synephrine blocked the dipsogenic response to administration of angiotensin II (200 micrograms/kg, SC). The antidipsogenic effect of both d,l-m-octopamine and l-m-synephrine could be blocked by concurrent administration of yohimbine (300 micrograms/kg, IP), an alpha 2-adrenoceptor antagonist. The results indicate that m-octopamine and m-synephrine exert their antidipsogenic effect via alpha 2-adrenoceptors. These studies add to a growing body of data suggesting that activation of alpha 2-adrenoceptors inhibits, while blockade of these receptors enhances, angiotensin II-induced drinking.

Octopamine action on the spontaneous contractions of the isolated nerve cord of Lumbricus terrestris

Octopamine and synephrine were observed to effect the spontaneous rhythmic contractions displayed by the isolated ventral nerve cord of the earthworm, Lumbricus terrestris. octopamine and synephrine produced dose-dependent significant changes in the frequency, amplitude and basal tonus of the spontaneous contractions. Application of adrenergic receptor antagonists suggested the octopamine receptors to have some similarity to vertebrate alpha 1-adrenergic receptors. The spontaneous contractions were not abolished by tetrodotoxin (TTX) which suggested a myogenic origin for the contraction of the ventral nerve cord sheath muscles. Octopamine, in the presence of TTX, increased the basal tonus and maximum force of the spontaneous contractions.

Multiple receptor types for octopamine in the locust

1. Three different pharmacological classes of octopamine receptor mediate the actions of octopamine on the locust extensor-tibiae neuromuscular preparation. A receptor classification scheme is proposed based on the results of detailed studies with agonists and antagonists. 2. Octopamine1 class receptors mediate the slowing of a myogenic rhythm found in a specialized proximal bundle of muscle fibres. Octopamine2A class receptors mediate the increase in amplitude of slow motoneurone twitch tension and octopamine2B class receptors mediate the increase in relaxation rate of twitch tension induced by firing either the fast or the slow motoneurones. 3. Octopamine1 receptors can be distinguished from the 2A and 2B classes since chlorpromazine (and yohimbine) are much better blocking agents than metoclopramide at the former receptors, whereas the converse is true for the latter class. Also clonidine is a more effective agonist than naphazoline for the former receptors and the converse is true for the latter class. 4. Octopamine 2A can be distinguished for octopamine 2B receptors since metoclopramide, mianserin and cyproheptadine show a strong preference for blocking the former class. Also naphazoline is a much better agonist than tolazoline at the former receptors and tolazoline is a much better agonist than clonidine at a latter. 5. The results are discussed in terms of the location of the various classes of octopamine receptors, their possible relationship to vertebrate alpha-adrenoreceptors, and the significance of the results for studies on octopamine receptors in the vertebrate central nervous system.

alpha-Sympathomimetic amines and calcium-mediated action potentials in guinea-pig ventricular muscle

1 The ability of amines, having alpha- or alpha- and beta-adrenoceptor stimulating activity, to restore excitability and contractility in heart preparations partially depolarized by potassium, was investigated in guinea-pig ventricular muscle in order to elucidate the mechanism of the positive inotropic effect mediated via alpha-adrenoceptors. 2 In preparations in which fast sodium channels were inactivated by K+-rich medium (22 mM) slow electrical responses as well as contractions were consistently induced by high concentrations of phenylephrine (10(-4) to 3 X 10(-4) M) and synephrine (3 X 10(-4) M). 3 The restorative effective effects of both phenylephrine and synephrine were unaffected by phentolamine (10(-5) M) but were readily abolished by practolol (10(-5) M) or sotalol (10(-5) M). 4 Methoxamine induced a dose-dependent positive inotropic effect in ventricular strips paced at 0.5 Hz in normal Tyrode solution; the maximum increase in contractile tension was obtained with methoxamine 10(-4) M. However, at the same concentration, the amine did not induce slow electrical responses in potassium-depolarized preparations. 5 It is concluded that the induction of slow responses by phenylephrine and synephrine is due to beta-adrenoceptor stimulation, and that the increase in cardiac contractility caused by alpha-adrenoceptor stimulation does not involve an increase in slow inward calcium current.

Drug-induced changes in catecholaminergic cells of the fish retina

The changes in fluorescence intensity and number of visible catecholaminergic cells (CA-cells), as revealed by means of a histofluorescence technique, were used as indicators of the effects of various pharmacological agents upon CA-cells in the retina of fishes (Cyprinus carpio and Eugerres plumieri). The study includes in vivo and in vitro experiments. In the in vivo experiments, intravitreal injection, two or three hours before eye enucleation, of 10 microgram L-DOPA, dopamine, or noradrenaline accentuated CA-cell fluorescence and increased the number of visible cells, whereas 10 microgram of tyramine, octopamine, synephrine, or adrenaline reduced the endogenous fluorescence. Intramuscular injection of reserpine (3 mg/kg) abolished CA-cell fluorescence. In the in vitro experiments, pieces of isolated retinas were incubated for three or 30 minutes in media containing different drugs. Only minor changes in fluorescence were detected after three minutes of incubation, but after 30 minutes, dopamine (20 microM) markedly enhanced CA-cell fluorescence. Carbachol (20 mM), acetylcholine (10 mM) plus BW-anticholinesterase (1 mM) or substance P(1.6 x 10(-2) mM), all reduced CA-cell fluorescence. Kainic acid (20 mM) abolished fluorescence from CA-cell somata, while fluorescent fiber networks remain unchanged. L-aspartate (5 mM) and GABA (10 mM) in the incubation medium did not influence fluorescence intensity. The results are relevant to, and consistent with, electrophysiological observations of dopamine-mediated spatial effects on horizontal cell potentials.

An alternative model for non-competitive antagonism

An antagonist acting on its own receptor leading to a gradual decrease in the affinity between an agonistic drug and its own but different receptor, is a metaffinoid antagonist. The presently published models for metaffinoid antagonism predict a parallel shift in the concentration-effect curves of the agonist by the metaffinoid antagonist, due to a gradual change in the affinity between the agonist and its receptor. An alternative model is proposed where the presence of an antagonist changes the affinity of only a fraction of the agonistic receptors, leading, in contrast to the presently published model to: a) non-parallel shifts in concentration-effect curves and b) metaffinoid antagonistic curves that look like the curves obtained in metactoid antagonism. Experimental support for the alternative model is found in the interaction between various beta-adrenergic agonists and serotonin in the guinea-pig tracheal chain and rat stomach fundus strip preparations.

Neural excitation of the larval firefly photocyte: slow depolarization possibly mediated by a cyclic nucleotide

1. In firefly larvae, extracellular recordings from the light organ nerve show that a volley of action potentials elicits a glow of an intact animal. 2. Intracellular recordings from the photocytes show that they respond to nerve stimulation with a slow, graded depolarization which precedes light emission. The depolarization begins about 0-5 s after the nerve is stimulated; it peaks about 1 s after stimulation; and subsides about 2-5 s after the stimulus. The glow increases fastest when the photocyte depolarization is at its peak and lasts 5–15 s. 3. Photocyte depolarization is associated with a decrease in the input resistance of the cell. 4. Adrenergic receptors in the light organ are pharmacologically similar to vertebrate alpha-receptors. 5. Phophodiesterase inhbitors, aminophylline and theophylline, cause the light organ to glow, suggesting that cyclic nucleotides may mediate the effect of the adrenergic nerve transmitter.

Estrogenic sensitivity of alpha-receptors in the urethra musculature

Estrogene has a tonicising effect upon urethra musculature. There is also the same demonstrable influence of alpha-receptor stimulating drugs upon the urethra pressure profile. After preliminary treatment with estrogene, there is a considerably stronger tonicising effect of alpha-stimulating drugs than without such a treatment. So the combination of estrogene and alpha-stimulating drugs seems a useful addition to the conservative treatment of stress incontinence.

[Blood-pressure regulating drugs and intraocular pressure in animal experiments (author's transl)]

Electromanometric measurements of blood pressure and intraocular pressure, carried out in rabbits after the intravenous administration of Norphen, Peripherin, Sympatol, Hydergin, Tropodil, Complamin, Euphyllin and Vasculat showed that the changes in the pressure curves were largely in the same sense. Apart from a "passive" correlation of the intraocular pressure with the blood pressure, the local effects of pharmaceuticals administered are also discussed. The results obtained provide both general medicine and ophthalmology with insights into the mode of action of drugs, some of which are frequently administered. In addition, they serve both to provide information on the desirable curative effects of the drugs and to help prevent damage being done to the organ of sight.