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PubMed1987

Analysis of monoamines and their metabolites by high performance liquid chromatography with coulometric electrochemical detection.

High performance liquid chromatography with coulometric electrochemical detection has been used to achieve simultaneous determination of norepinephrine, epinephrine, 5-hydroxytryptophan, normetanephrine, dopamine, metanephrine, 3,4-dihydroxyphenylacetic acid, N-acetyldopamine, tyramine, tryptophan, 5-hydroxyindoleacetic acid, 5-hydroxytryptamine, N-acetyl-5-hydroxytryptamine, homovanillic acid, tyrosine, p-octopamine, N-acetyl-p-octopamine, and p-synephrine. The procedure has been applied to study monoamine degradation in the insect brain and to demonstrate that N-acetylation rather than oxidative deamination is the primary route of monoamine catabolism in insects.

Animals↗
PubMed1996

Insect neurotransmission: neurotransmitters and their receptors.

The roles of acetylcholine, dopamine, octopamine, tyramine, 5-hydroxytryptamine, histamine, glutamate, 4-aminobutanoic acid (gamma-aminobutyric acid) and a range of peptides as insect neurotransmitters are evaluated in terms of the criteria used to identify transmitters. Of the biogenic amines considered, there is good evidence that acetylcholine, dopamine, octopamine, 5-hydroxytryptamine, and histamine should be considered to be neurotransmitters, but the case for tyramine is less convincing at the moment. The evidence supporting neurotransmitter roles for glutamate and gamma-aminobutyric acid at specific insect synapses is overwhelming, but much work remains to be undertaken before the full significance of these molecules in the insect nervous system is appreciated. Attempts to characterise biogenic amine and amino acid receptors using pharmacological and molecular biological techniques have revealed considerable differences between mammalian and insect receptors. The number of insect neuropeptides isolated and identified has increased spectacularly in recent years, but genuine physiological or biochemical functions can be assigned to very few of these molecules. Of these, only proctolin fulfills the criteria expected of a neurotransmitter, and the recent discovery of proctolin receptor antagonists should enable the biology of this pentapeptide to be explored fully.

Animals↗
PubMed1983

Inhibition of dihydropteridine reductase by catecholamines and related compounds.

Catecholamines and related compounds, such as dopamine, 5- or 6-hydroxydopamine, N-methyldopamine, tyramine, octopamine, norepinephrine and epinephrine, inhibit human liver dihydropteridine reductase (NADH:6,7-dihydropteridine oxidoreductase, EC 1.6.99.10) noncompetitively with Ki values ranging from 7.0 X 10(-6) - 1.9 X 10(-4)M (I50 values = 2.0 X 10(-5) - 2.0 X 10(-4)M). The tyrosine analogs alpha-methyltyrosine and 3-iodotyrosine are weak inhibitors of this enzyme (I50 greater than 10(-3)M). The inhibitory effect of catecholamines is slightly decreased by O-methylation of one hydroxyl group, but is essentially abolished by total methylation. The inhibitory strength of the catecholamines and related compounds tested against this enzyme can be arranged in the following order: dopamine, 6-hydroxydopamine, 5-hydroxydopamine, N-methyldopamine greater than tyramine, 3-O-methyldopamine, 4-O-methyldopamine much greater than epinephrine, 3-O-methylepinephrine, norepinephrine, octopamine less than tyrosine much less than alpha-methyltyrosine, 3-iodotyrosine much less than homoveratrylamine. These results suggest that dopamine, norepinephrine and epinephrine may serve as physiological regulators of mammalian dihydropteridine reductase.

Catecholamines↗
PubMed1989

Further characterisation of the dopamine-inhibitory receptor in Helix and evidence for a noradrenaline-preferring receptor.

1. The cells in this study responded with a hyperpolarization to the following agents in this order of potency; dopamine greater than noradrenaline phenylephrine = octopamine. 2. 6,7 ADTN had a relative potency of 0.1 compared to dopamine. 5,6 ADTN did not inhibit the cells in this study. 3. The D1 receptor agonists SKF38393 and dihydroxynomifensine mimicked the effect of dopamine on these cells but were over 100 times less active, whereas the D2 selective agonists quinpirole and RU24213 were without effect. 4. Both the D1 antagonist SCH23390 and the D2 antagonist sulpiride antagonised the dopamine response with pA2 values of 6.1 and 6.7, respectively. 5. Five cells that responded to dopamine with a hyperpolarization were depolarized by noradrenaline. The order of potency of compounds at eliciting this depolarization, noradrenaline greater than phenylephrine greater than octopamine indicated that this response may be mediated by a noradrenaline-preferring receptor.

Animals↗
PubMed2004

Evidence for a possible neurotransmitter/neuromodulator role of tyramine on the locust oviducts.

Visualization of the tyraminergic innervation of the oviducts was demonstrated by immunohistochemistry, and the presence of tyramine was confirmed using high-performance liquid chromatography coupled to electrochemical detection. Oviducts incubated in high-potassium saline released tyramine in a calcium-dependent manner. Stimulation of the oviducal nerves also resulted in tyramine release, suggesting that tyramine might function as a neurotransmitter/neuromodulator at the locust oviducts. Tyramine decreased the basal tension, and also attenuated proctolin-induced contractions in a dose-dependent manner over a range of doses between 10(-7) and 10(-4) M. Low concentrations of tyramine attenuated forskolin-stimulated cyclic AMP levels in a dose-dependent manner. This effect was not blocked by yohimbine. High concentrations of tyramine increased basal cyclic AMP levels of locust oviducts in a dose-dependent manner; however, the increases in cyclic AMP were only evident at the highest concentrations tested, 5 x 10(-5) and 10(-4) M tyramine. The tyramine-induced increase in cyclic AMP shared a similar pharmacological profile with the octopamine-induced increase in cyclic AMP. Tyramine increased the amplitude of excitatory junction potentials at low concentrations while hyperpolarizing the membrane potential by 2-5 mV. A further increase in the amplitude of the excitatory junction potentials and the occurrence of an active response was seen upon washing tyramine from the preparation. These results suggest that tyramine can activate at least three different endogenous receptors on the locust oviducts a putative tyramine receptor at low concentrations, a different tyramine receptor to inhibit muscle contraction, and an octopamine receptor at high concentrations.

Adrenergic alpha-Antagonists↗
PubMed2004

Monoamines directly inhibit N-methyl-D-aspartate receptors expressed in Xenopus oocytes in a voltage-dependent manner.

Dopamine has numerous functions in the brain and has been shown to modulate responses of N-methyl-D-aspartate (NMDA) receptors on thalamic and hippocampus neurons [N.G. Castro, M.C.F. de Mello, F.G. de Mello, Y. Aracava, Direct inhibition of the N-methyl-D-aspartate receptor channel by dopamine and (+)-SKF38393, Br. J. Pharmacol. 126 (1999) 1847-1855]. Thus, the effects of dopamine, serotonin, tyramine, epinephrine, norepinephrine, and octopamine on NMDA receptors were studied using voltage-clamp recording of recombinant NMDA receptors expressed in Xenopus oocytes. Serotonin and tyramine, in addition to dopamine, were found to inhibit macroscopic currents at heteromeric NMDA receptors, but not AMPA (GluR1/GluR2) receptors. Epinephrine, norepinephrine and octopamine also weakly inhibited macroscopic currents at NR1/NR2A and NR1/NR2B receptors. The inhibitory effects of these monoamines became prominent at -100 mV comparing those at -20 mV. Mutations at NR1 N616, NR2B N615, and NR2B N616, but not at NR1 W563 and NR1 N650, reduced the inhibitory effects by monoamines. These results indicate that these monoamines directly act on the narrowest region of channel pore.

Animals↗
PubMed1982

Assay for dopamine beta-hydroxylase in rat serum and adrenal medulla by high-performance liquid chromatography with fluorescence detection.

A highly sensitive method for the assay of dopamine beta-hydroxylase in rat serum and in sample solution prepared from rat adrenal medulla is described which employs high-performance liquid chromatography with fluorescence detection. Octopamine, formed enzymatically from the substrate tyramine, is separated by Dowex 50/-X4 column chromatography and oxidized with periodate to p-hydroxybenzaldehyde, which is then converted into a fluorescent compound with 2,2'-dithiobis(1-aminonaphthalene). The derivative, after extraction with n-hexane--chloroform, is separated by normal-phase chromatography on Alox T. The limit of detection for octopamine formed enzymatically is 10 pmol. This method requires as little as 5 microliter of rat serum.

Adrenal Medulla↗
PubMed1989

Analysis of biogenic amines in the brain of the American cockroach (Periplaneta americana) by gas chromatography-negative ion chemical ionisation mass spectrometry.

Biogenic amines in the brain of the American cockroach have been identified and quantified by an extraction-derivatisation procedure involving their reaction with ditrifluoromethylbenzoyl chloride (DTFMB) in the aqueous phase followed by extraction into an organic solvent, hydrolysis of phenolic esters and conversion of free hydroxyl groups to trimethylsilyl (TMS) ethers and subsequent analysis by gas chromatography-negative ion chemical ionisation mass spectrometry. The molecular ion of these DTFMB-TMS derivatives carried most of the ion current which made the method highly specific and gave a potential limit of detection below the picogram level. This method establishes unequivocally that the principal amines in cockroach brain are tyramine, p-octopamine, dopamine, 5-hydroxytryptamine and noradrenaline. In contrast to mammalian nervous tissue, the other positional isomers of octopamine, together with the isomeric synephrines, are absent.

Animals↗
PubMed2002

Unusual genetic architecture of natural variation affecting drug resistance in Drosophila melanogaster.

Naturally occurring genetic variation was quantified for survival time of adult Drosophila melanogaster exposed to chronic ingestion of the drugs nicotine, caffeine, dopamine, tyramine and octopamine. Responses to nicotine, tyramine and octopamine were genetically correlated in both sexes, whereas caffeine response correlated with starvation resistance. However, there is also genetic variation that is specific for each of the drugs. Females tended to be more resistant than males to nicotine and caffeine but sex-by-genotype interactions were also seen for these drugs and for the response to dopamine. An unusual and complex genetic architecture was observed in crosses between lines with different responses to caffeine ingestion. Additive and dominance components were clearly seen from the analysis of F1 individuals, but increased female resistance to caffeine in backcross generations and increased male sensitivity in F2 generations confused the interpretation of possible epistatic contributions.

Analysis of Variance↗
PubMed2005

Analysis of biogenic amine variability among individual fly heads with micellar electrokinetic capillary chromatography-electrochemical detection.

Neurochemical variability among individual Drosophila heads has been examined with the sensitivity of electrochemical detection and the selectivity of micellar electrokinetic capillary chromatography. Homogenization of single Drosophila heads in volumes as small as 100 nL has been accomplished. Here we demonstrate reproducible separations for single fly heads in 250-nL volumes providing a 4-fold increase in sensitivity without overloading the electrochemical detector. This increase in sensitivity allows detection of previously undetected analytes, such as N-acetyltyramine (naTA) and octopamine (OA). Analytes including L-3,4-dihydroxyphenylalanine, N-acetyl octopamine, N-acetyldopamine, naTA, N-acetylserotonin, OA, dopamine, tyramine, and serotonin also have been consistently identified in single-head homogenates and observed with homogenates representing populations of Drosophila. Neurochemical variation between individual flies as well as the consistency within a population indicates varying amounts of neurotransmitter turnover. The inception, design, and fabrication of a miniature tissue homogenizer has enabled the separation of biogenic amines and metabolites from these severely volume-limited single Drosophila head homogenates.

Animals↗
PubMed1980

Synthesis and structure-activity relationships among alpha-adrenergic receptor agonists of the phenylethanolamine type.

Nineteen arylethanolamine derivatives related to norepinephrine were prepared and tested for alpha-adrenergic stimulant activity. In one series the analogues possess a p-hydroxy function, while the meta position is substituted by methyl, ethyl, isopropyl, chlohexyl, fluoro, chloro, iodo, carboxy, carbomethoxy, and methylsulfamido groups. The other series is meta hydroxylated with the para position substituted by the same groups. The influence of these groups upon the alpha-adrenergic activity is discussed, and the compounds are compared to octopamine, normetanephrine, norepinephrine, and norphenylephrine. It has been found that the introduction of an isopropyl, cyclohexyl, and fluoro group in the meta position of octopamine improves its affinity by three, five, and six times, respectively, whereas when these groups are introduced in the para position of norphenylephrine their effects are always detrimental. The most active compound, alpha-(aminomethyl)(4-fluoro-3-hydroxyphenyl)methanol (44), has about one-hundredth the affinity and the same intrinsic activity as norepinephrine.

Adrenergic alpha-Agonists↗
PubMed2005

The hangover gene defines a stress pathway required for ethanol tolerance development.

Repeated alcohol consumption leads to the development of tolerance, simply defined as an acquired resistance to the physiological and behavioural effects of the drug. This tolerance allows increased alcohol consumption, which over time leads to physical dependence and possibly addiction. Previous studies have shown that Drosophila develop ethanol tolerance, with kinetics of acquisition and dissipation that mimic those seen in mammals. This tolerance requires the catecholamine octopamine, the functional analogue of mammalian noradrenaline. Here we describe a new gene, hangover, which is required for normal development of ethanol tolerance. hangover flies are also defective in responses to environmental stressors, such as heat and the free-radical-generating agent paraquat. Using genetic epistasis tests, we show that ethanol tolerance in Drosophila relies on two distinct molecular pathways: a cellular stress pathway defined by hangover, and a parallel pathway requiring octopamine. hangover encodes a large nuclear zinc-finger protein, suggesting a role in nucleic acid binding. There is growing recognition that stress, at both the cellular and systemic levels, contributes to drug- and addiction-related behaviours in mammals. Our studies suggest that this role may be conserved across evolution.

Alcoholism↗
PubMed2006

Trace amine-associated receptors and their ligands.

Classical biogenic amines (adrenaline, noradrenaline, dopamine, serotonin and histamine) interact with specific families of G protein-coupled receptors (GPCRs). The term 'trace amines' is used when referring to p-tyramine, beta-phenylethylamine, tryptamine and octopamine, compounds that are present in mammalian tissues at very low (nanomolar) concentrations. The pharmacological effects of trace amines are usually attributed to their interference with the aminergic pathways, but in 2001 a new gene was identified, that codes for a GPCR responding to p-tyramine and beta-phenylethylamine but not to classical biogenic amines. Several closely related genes were subsequently identified and designated as the trace amine-associated receptors (TAARs). Pharmacological investigations in vitro show that many TAAR subtypes may not respond to p-tyramine, beta-phenylethylamine, tryptamine or octopamine, suggesting the existence of additional endogenous ligands. A novel endogenous thyroid hormone derivative, 3-iodothyronamine, has been found to interact with TAAR1 and possibly other TAAR subtypes. In vivo, micromolar concentrations of 3-iodothyronamine determine functional effects which are opposite to those produced on a longer time scale by thyroid hormones, including reduction in body temperature and decrease in cardiac contractility. Expression of all TAAR subtypes except TAAR1 has been reported in mouse olfactory epithelium, and several volatile amines were shown to interact with specific TAAR subtypes. In addition, there is evidence that TAAR1 is targeted by amphetamines and other psychotropic agents, while genetic linkage studies show a significant association between the TAAR gene family locus and susceptibility to schizophrenia or bipolar affective disorder.

Amino Acids↗
PubMed2006

Expression of Caenorhabditis elegans neurotransmitter receptors and ion channels in Xenopus oocytes.

Injection of Caenorhabditis elegans polyA RNA into Xenopus laevis oocytes led to the expression of neurotransmitter receptors that generated some unique responses, including ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors as well as receptors that coupled to G proteins, such as those to octopamine, norepinephrine, and angiotensin, which activated the oocyte's own phosphatidylinositol system and calcium-gated chloride channels. The oocytes also expressed chloride-conducting glutamate receptors, muscarinic acetylcholine receptors, and voltage-operated calcium channels. Unexpectedly, serotonin (5-hydroxytryptamine), dopamine, GABA, and kainate did not generate ionic currents, suggesting that the corresponding receptors were not expressed or were not functional in the oocytes. The use of X. laevis oocytes for expressing worm RNA demonstrates that there are many molecular components whose role remains to be clarified in the nematode. Among them are the nature of the endogenous agonists for the octopamine and angiotensin receptors and the subunits that compose the ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and the norepinephrine receptors that couple to the phosphoinositide cascade.

Animals↗
PubMed1990

Formamidines as synergists of cypermethrin in susceptible and pyrethroid resistant house flies (Diptera: Muscidae).

Mechanisms of formamidine synergism of pyrethroid insecticides were investigated in the house fly, Musca domestica L. A bioassay method was developed to show formamidine synergism of cypermethrin in adult house flies. Flies were exposed to a residue of cypermethrin with and without formamidine for 30 min and then transferred to a clean container. Mortality was recorded 24 h later. Synergism of cypermethrin occurred in flies exposed simultaneously to cypermethrin plus formamidines and in flies exposed to cypermethrin either before or after exposure to a formamidine. Synergism ranged up to 11.8-fold and was greater in susceptible than in resistant house flies. A monomeric derivative of amitraz (BTS 27271) was the most active synergist, chlordimeform was intermediate, and amitraz was least active. Synergism of cypermethrin also occurred in flies injected with octopamine and then exposed to cypermethrin, suggesting that formamidines may be acting as octopamine agonists. Measurements of the effects of formamidines on uptake of cypermethrin showed that BTS 27271 increased uptake less than chlordimeform and that amitraz had almost no effect. Both target site and behavioral effects are discussed as possible mechanisms of formamidine synergism of cypermethrin and other pyrethroids.

Amidines↗
PubMed1999

Cholinergic synaptic transmission in insect mushroom bodies in vitro.

The mushroom body of the bee brain is an important site for learning and memory. Here we investigate synaptic transmission in the mushroom body using extracellular recording techniques in a whole bee brain in vitro preparation. The postsynaptic response showed attenuation by cadmium and paired-pulse facilitation, similar to in vivo findings. This confirms the viability of the in vitro preparation and supports the isolated whole bee brain as a useful model of the in vivo preparation. Bath application of the acetylcholine receptor antagonists, D-tubocurarine and alpha-bungarotoxin attenuated the postsynaptic response by 61 and 62% of control, respectively. The glutamate receptor antagonists, (+)-2-amino-5-phosphonopentanoic acid and 6-cyano-7-nitroquinoxaline-2,3-dione, had no effect. The invertebrate monoamine and neuromodulator, octopamine, transiently increased the postsynaptic response by 130% of control. These results suggest that synaptic transmission of the olfactory input pathway in the mushroom body is 1) mediated primarily by acetylcholine and 2) modulated by octopamine.

Acetylcholine↗
PubMed2002

Modulating the modulators: parasites, neuromodulators and host behavioral change.

Neuromodulators can resculpt neural circuits, giving an animal the behavioral flexibility it needs to survive in a complex changing world. This ability, however, provides parasites with a potential mechanism for manipulating host behavior. This paper reviews three invertebrate host-parasite systems to examine whether parasites can change host behavior by secreting neuromodulators. The parasitic wasp, Cotesia congregata, suppresses host feeding partly by inducing the host (Manduca sexta) to increase the octopamine concentration in its hemolymph. The increased octopamine concentration disrupts the motor pattern produced by the frontal ganglion, preventing the ingestion of food. Polymorphus paradoxus (Acanthocephalan) alters the escape behavior of its host, Gammarus lacustris (Crustacea), possibly through an effect on the host's serotonergic system. The trematode Trichobilharzia ocellata inhibits egg-laying in its snail host (Lymnaea stagnalis), partly by inducing the host to secrete schistosomin. Schistosomin decreases electrical excitability of the caudodorsal cells. The parasite also alters gene expression for some neuromodulators within the host's central nervous system. In at least two of these three examples, it appears that the host, not the parasite, produces the neuromodulators that alter host behavior. Producing physiologically potent concentrations of neuromodulators may be energetically expensive for many parasites. Parasites may exploit indirect less energetically expensive methods of altering host behavior. For example, parasites may induce the host's immune system to produce the appropriate neuromodulators. In many parasites, the ability to manipulate host behavior may have evolved from adaptations designed to circumvent the host's immune system. Immune-neural-behavioral connections may be pre-adapted for parasitic manipulation.

Animals↗
PubMed1995

Non-linear dynamics of neurochemical modulation of mosquito oviduct and hindgut contractions.

Microphysiological techniques and computer-based methods of data acquisition and analysis were used to investigate the dynamics of neurochemical action on spontaneous contractions of continuously perfused oviducts and hindguts isolated from female mosquitoes (Aedes aegypti). Proctolin, leucomyosuppressin (LMS), serotonin and octopamine, which are known to modulate insect muscle contractions, and a mosquito neuropeptide, Aedes Head Peptide I (Aea-HP-I), which inhibits host-seeking behavior, were tested in the bioassays. LMS depressed contractile activity in oviducts at concentrations above 10(-12) mol l-1, but hindguts did not respond to concentrations below 10(-6) mol l-1. Hindgut contractions spontaneously restarted in 10(-6) mol l-1 LMS, but only washing out LMS restored activity in oviducts. LMS changed the amplitude of the oviduct contractions, but the dynamics of contraction remained steady. Following recovery of contractions in LMS, hindgut tissues contracted with a more regular pattern. Serotonin and octopamine had an identical action on oviduct and hindgut tissues. At concentrations greater than 10(-8) mol l-1, serotonin eliminated the refractory period between contractions and thus increased the contraction frequency of oviducts. Though the contractions appeared chaotic, state-series analysis proved that serotonin-treated oviducts contracted rhythmically. Above 10(-6) mol l-1, serotonin extinguished normal hindgut peristalsis and induced regular fluttering of the anteriormost portion of the hindgut, an effect possibly related to diuresis following the blood meal. Proctolin failed to stimulate both oviduct and hindgut contractions at concentrations up to 10(-6) mol l-1, but at 10(-8) mol l-1 induced contractions of cricket hindgut preparations. Aea-HP-I had no effect on either tissue at 10(-6) mol l-1 or lower concentrations. State-series analysis, based on simple manipulations of experimental data, permitted direct observation of the dynamics of oviduct and hindgut contractile activity.

Aedes↗