ABSTRACT
Large systems of coupled oscillators subjected to a periodic external drive occur in many situations in physics and biology. Here the simple paradigmatic case of equal strength, all-to-all sine coupling of phase oscillators subject to a sinusoidal external drive, is considered. The stationary states and their stability are determined. Using the stability information and numerical experiments, parameter space phase diagrams showing when different types of system behavior apply are constructed, and the bifurcations marking transitions between different types of behavior are delineated. The analysis is supported by results of direct numerical simulation of an ensemble of oscillators.
Subject(s)
Algorithms , Biological Clocks/physiology , Metabolic Networks and Pathways/physiology , Models, Theoretical , Nerve Net/physiology , Nonlinear Dynamics , Oscillometry/methods , Computer Simulation , Feedback , PeriodicityABSTRACT
Selective radioligands for histamine H(3) receptors have been used to characterize H(3) receptor pharmacology by radioligand binding assays and to determine H(3) receptor distribution by tissue autoradiography. Here we report the synthesis and receptor binding characterization of [(3)H]A-317920 (furan-2-carboxylic acid(2-[4-[3-([3,5-(3)H]4-cyclopropanecarbonyl-phenoxy)-propyl]-piperazin-1-yl]-1-methyl-2-oxo-ethyl)-amide), a high affinity inverse agonist radioligand for the rat H(3) receptor. The binding of [(3)H]A-317920 to rat cortical and cloned H(3) receptors revealed fast on- and slower off-rate kinetics with calculated K(d) values in agreement with those determined in saturation binding assays (0.2 nM for both receptors). Further, we compared [(3)H]A-317920 with the agonist [(3)H](N)-alpha-methylhistamine ([(3)H]NalphaMH) as radioligand tools to study receptor pharmacology. Agonists and antagonists displaced [(3)H]NalphaMH with one-site binding characteristics and Hill slopes approached unity. In contrast, although antagonists exhibited one-site binding, [(3)H]A-317920 displacement by agonists was best fit by two-site binding models, and the potencies of the high affinity, GDP-sensitive sites correlated with the potencies defined in [(3)H]NalphaMH binding. Unlike [(125)I]iodoproxyfan, [(3)H]A-317920 exhibits potent and selective binding to rat H(3) receptors with low binding to non-H(3) sites, including cytochrome P450. These findings show that [(3)H]A-317920 is a potent rat H(3) receptor antagonist radioligand and has utility for studying H(3) receptor pharmacology.
Subject(s)
Piperazines/metabolism , Receptors, Histamine H3/physiology , Animals , Cell Membrane/physiology , Cerebral Cortex/physiology , Cloning, Molecular , Humans , Kinetics , Piperazines/pharmacology , Radioligand Assay , Rats , Receptors, Histamine H3/drug effects , Receptors, Histamine H3/genetics , Recombinant Proteins/antagonists & inhibitors , Recombinant Proteins/metabolism , TritiumSubject(s)
Benzofurans/pharmacology , Cognition/drug effects , Histamine Antagonists/pharmacology , Pyrrolidines/pharmacology , Receptors, Histamine H3/metabolism , Schizophrenia/drug therapy , Schizophrenia/metabolism , Animals , Benzofurans/therapeutic use , Cognition/physiology , Histamine Antagonists/therapeutic use , Memory/drug effects , Memory/physiology , Mice , Mice, Inbred DBA , Models, Animal , Pyrrolidines/therapeutic use , Rats , Rats, WistarSubject(s)
Biphenyl Compounds/pharmacology , Histamine Antagonists/pharmacology , Nitriles/pharmacology , Obesity/metabolism , Obesity/prevention & control , Pyrrolidines/pharmacology , Receptors, Histamine H3/metabolism , Animals , Biphenyl Compounds/adverse effects , Biphenyl Compounds/chemistry , Diet , Dietary Fats/administration & dosage , Dietary Fats/pharmacology , Histamine Agonists/chemistry , Histamine Agonists/pharmacology , Histamine Antagonists/adverse effects , Histamine Antagonists/chemistry , Male , Mice , Mice, Inbred C57BL , Molecular Structure , Nitriles/adverse effects , Nitriles/chemistry , Obesity/chemically induced , Pyrrolidines/adverse effects , Pyrrolidines/chemistrySubject(s)
Biphenyl Compounds/pharmacology , Histamine Agonists/pharmacology , Piperazines/pharmacology , Receptors, Histamine H3/metabolism , Animals , Biphenyl Compounds/chemistry , Cell Line , Histamine Agonists/chemistry , Humans , Imidazoles/chemistry , Molecular Structure , Piperazines/chemistry , Radioligand Assay , RatsSubject(s)
Histamine Antagonists/pharmacology , Piperazines/pharmacology , Receptors, Histamine H3/drug effects , 1-Methyl-3-isobutylxanthine/pharmacology , Binding, Competitive/drug effects , Colforsin/pharmacology , Cyclic AMP/metabolism , Histamine Agonists/metabolism , Humans , Ligands , Methylhistamines/metabolism , Phosphodiesterase Inhibitors/pharmacology , Receptors, Histamine H3/metabolismSubject(s)
Histamine Antagonists/chemical synthesis , Histamine Antagonists/pharmacology , Piperazines/chemical synthesis , Piperazines/pharmacology , Receptors, Histamine H3/drug effects , Alanine/chemistry , Amides/chemistry , Animals , Binding, Competitive/drug effects , Humans , Indicators and Reagents , Kinetics , Rats , Recombinant Proteins/metabolismABSTRACT
ABT-229 (8,9-anhydro-4"-deoxy-3'-N-desmethyl-3'-N-ethylerythromycin B-6,9-hemiacetal), a synthetic derivative of erythromycin (ERY) with no antibiotic activity, has been shown to bind to motilin receptors and stimulate contractile activity of the antrum and small intestine. The objective of this study was to determine the effect of ABT-229 on canine gastric emptying (GE) and contractile activity of the antrum and duodenum in response to a solid meal. Six beagles were used to determine GE of a solid meal and contractile activity in response to either vehicle, ABT-229 (0.17, 0.83, 2.5, or 5.0 microg/kg/min), ERY (33.3 microg/kg/min), or cisapride (CIS) (10 microg/kg/min). Lag (t(lag)), half-emptying (t(1/2)), and complete emptying (t(full)) times were determined. Contractile data were analyzed for motility index and gastroduodenal coordination. Compared with vehicle, ABT-229 dose dependently accelerated GE, t(lag) was decreased at the two highest doses, t(1/2) was decreased compared with vehicle at the three highest doses, and t(full) was decreased at all doses compared with vehicle. ERY also decreased t(1/2) and t(full), whereas CIS decreased all GE parameters. The slopes of the linear phase of GE curves for all drugs and doses were greater than those for vehicle. ABT-229 dose dependently increased the motility index as well as gastroduodenal coordination. ABT-229 (two highest doses) and CIS accelerated GE of a solid meal by decreasing the lag phase and increasing the rate of GE, whereas ERY only increased the rate of GE. The data suggest that ABT-229 is 7- to 40-fold more potent than ERY in accelerating GE.
Subject(s)
Cisapride/pharmacology , Erythromycin/analogs & derivatives , Erythromycin/pharmacology , Gastric Emptying/drug effects , Gastrointestinal Agents/pharmacology , Animals , Dogs , Dose-Response Relationship, Drug , Gastrointestinal Motility/drug effects , Muscle Contraction/drug effectsABSTRACT
In our quest toward the discovery of highly potent and acid-stable motilides, novel 4"-deoxy derivatives of 9-deoxo-6, 9-epoxyerythromycin were designed, synthesized, and evaluated for their gastrointestinal prokinetic activities. These compounds, in their 9R configuration, were more potent than their 6,9-enol ether homologues in inducing well-coordinated smooth muscle contractions in an in vitro rabbit duodenal assay: e.g., (9R), (8S)-9-deoxo-4"-deoxy-3'-N-desmethyl-3'-N-ethyl-6, 9-epoxyerythromycin A (10) and (9R), (8S)-9-deoxo-4"-deoxy-3'-N-desmethyl-3'-N-ethanol-6, 9-epoxyerythromycin A (15) had a pED50 of 8.54 and 8.11 compared to a pED50 of 7.22 for compound 2 (ABT-229). Reduction of the 6,9-enol ether, which was aimed at improving the acid stability, afforded the most stable motilides to date with t1/2 of 5.5 h for 10 and 15. Compounds 10 and 15 bind specifically to rabbit antral smooth muscle motilin receptors with pIC50 values of 8.52 and 8.70.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Erythromycin/analogs & derivatives , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/metabolism , Anti-Bacterial Agents/pharmacology , Drug Design , Drug Stability , Duodenum/drug effects , Duodenum/physiology , Erythromycin/chemical synthesis , Erythromycin/chemistry , Erythromycin/metabolism , Erythromycin/pharmacology , Escherichia coli/drug effects , Hydrogen-Ion Concentration , In Vitro Techniques , Male , Models, Molecular , Molecular Conformation , Muscle Contraction/drug effects , Muscle, Smooth/drug effects , Muscle, Smooth/physiology , Pyloric Antrum/metabolism , Rabbits , Receptors, Gastrointestinal Hormone/metabolism , Receptors, Neuropeptide/metabolism , Staphylococcus aureus/drug effects , Stereoisomerism , Streptococcus/drug effectsABSTRACT
A series of new, highly potent and orally active "motilactides", 9-deoxo-4"-deoxy-6,9-epoxyerythromycin lactams was designed, synthesized, and evaluated for their gastrointestinal motor stimulating activity. These compounds were acid stable and showed good oral efficacy.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Epoxy Compounds/chemical synthesis , Erythromycin/analogs & derivatives , Erythromycin/chemical synthesis , Myoelectric Complex, Migrating/drug effects , Administration, Oral , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Biological Availability , Dogs , Epoxy Compounds/chemistry , Epoxy Compounds/pharmacology , Erythromycin/chemistry , Erythromycin/pharmacology , Indicators and Reagents , Molecular Structure , Myoelectric Complex, Migrating/physiology , Prodrugs/chemical synthesis , Prodrugs/chemistry , Prodrugs/pharmacology , Receptors, Gastrointestinal Hormone/agonists , Receptors, Neuropeptide/agonists , Structure-Activity RelationshipABSTRACT
As an approach to discovering highly potent motilides with oral activity, novel 4"-deoxy derivatives of 8,9-anhydroerythromycin 6,9-hemiacetal were designed, synthesized, and evaluated for their gastrointestinal prokinetic activities. These compounds were orders of magnitude more potent than their 4"-hydroxy analogs in inducing smooth muscle contractions in an in vitro rabbit duodenal assay. Removal of the 12-hydroxy group, which was aimed at improving oral bioavailability, also afforded further potentiation in in vitro activity, leading to the identification of 8,9-anhydro-4"-deoxy-3'-N-desmethyl-3'-N-ethylerythromycin B 6,9-hemiacetal (ABT-229) as a potential prokinetic drug. ABT-229 was > 300,000 times more potent than erythromycin in vitro and had 39% oral bioavailability in dog compared to its 4",12-dihydroxy congener (EM-523), which was only 400 times more potent than erythromycin and had relatively low (1.4%) oral bioavailability.
