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PubMed1974

Simulation of biogenic amine metabolism in the brain.

The metabolism of a number of biogenic amines has been simulated by using data obtained from studies of the individual enzymes from pig brain. It is shown that beta-hydroxylated amines such as noradrenaline and octopamine are metabolized primarily to the alcoholic metabolite whereas amines lacking this group [e.g. dopamine (3,4-dihydroxyphenethylamine) and 5-hydroxytryptamine] are metabolized at low concentrations to give the corresponding acid. Increase in the amine concentration results in an increase in the proportion of the alcoholic metabolite formed and this may in part account for the effects of the drug reserpine on amine metabolism. The effects of disulfiram (Antabuse) and ethanol (acting through its metabolite acetaldehyde) on amine metabolism may be understood in terms of this simulated model. It is shown that drugs that affect this system also cause alterations in the steady-state concentrations of the intermediate aldehydes and the possible implications of this are discussed.

Animals↗
PubMed2002

Modulation by 5-hydroxytryptamine of nicotinic acetylcholine responses recorded from an identified cockroach (Periplaneta americana) motoneuron.

Recordings from the soma of the cockroach (Periplaneta americana) fast coxal depressor motoneuron (Df) were made while acetylcholine (ACh) was regularly pressure-applied locally from a micropipette. The modulatory effects upon these nicotinic ACh responses of bath-applied 5-hydroxytryptamine (5-HT, serotonin), dopamine and octopamine were investigated under either current-clamp or voltage-clamp conditions. The biogenic amines reversibly suppressed, but never totally abolished, ACh responses, 5-HT being the most potent, with a threshold near 10(-6) m (EC50 = 5 x 10(-5) m). Occlusion experiments indicate that the amines share a common mechanism at the level of either receptors or second messenger pathways. The amines also modulated responses to nicotine or carbachol (each of which resists hydrolysis by acetylcholinesterases), indicating that the amines did not act by accelerating ACh degradation. Pharmacological antagonists were used in an attempt to characterize the receptor responsible for amine-mediated modulation. Although a number of antagonists mimicked the action of amines rather than producing blockade, the antagonistic actions of LSD and RS23597 pointed strongly to a receptor-mediated mechanism, but did not allow receptor identification. The magnitude of the modulatory effect of 5-HT was significantly reduced by intracellular guanosine-5'-O-(2-thiodiphosphate) (GDP-beta-S), indicating involvement of a G-protein. Intracellular injection of the calcium chelator BAPTA did not block the modulatory effect of 5-HT, showing that the amines do not operate through the calcium-dependent pathway by which muscarinic receptors act on nicotinic currents. The adenylate cyclase inhibitor dideoxyadenosine (DDA), on the other hand, did attenuate the action of 5-HT, suggesting involvement of cyclic AMP.

Acetylcholine↗
PubMed2003

B96Bom encodes a Bombyx mori tyramine receptor negatively coupled to adenylate cyclase.

A cDNA encoding a biogenic amine receptor (B96Bom) was isolated from silkworm (Bombyx mori) larvae, and the ligand response of the receptor stably expressed in HEK-293 cells was examined. Tyramine (TA) at 0.1-100 micro m reduced forskolin (10 micro m)-stimulated intracellular cAMP levels by approximately 40%. The inhibitory effect of TA at 1 micro m was abolished by yohimbine and chlorpromazine (each 10 micro m). Although octopamine (OA) also reduced the cAMP levels, the potency was at least two orders of magnitude lower than that of TA. Furthermore, unlabelled TA (IC50 = 5.2 nm) inhibited specific [3H]TA binding to the membranes of B96Bom-transfected HEK-293 cells more potently than did OA (IC50 = 1.4 micro m) and dopamine (IC50 = 1.7 micro m). Taken together with the result of phylogenetic analysis, these findings indicate that the B96Bom receptor is a B. mori TA receptor, which is negatively coupled to adenylate cyclase. The use of this expression system should facilitate physiological studies of TA receptors as well as structure-activity studies of TA receptor ligands.

Adenylyl Cyclases↗
PubMed1997

Adrenergic neurotransmitters and calcium ionophore-induced situs inversus viscerum in Xenopus laevis embryos.

Xenopus laevis embryos at the blastula-early tail bud stage were exposed to norepinephrine or octopamine dissolved in culture saline until they reached the larval stage. The left-right asymmetry of the heart and gut was then examined. We found that these adrenergic neurotransmitters induced situs inversus in the heart and/or gut in up to 35% of tested neurula embryos. Norepinephrine-induced situs inversus was blocked by the alpha-1 adrenergic antagonist prazosin. Furthermore, A23187, a calcium ionophore, also increased the incidence of situs inversus up to 54% when late-neurula embryos were exposed to the solution. A23187 treatment initiated before neural groove formation was less effective. The incidence of situs inversus induced by these reagents decreased towards the control level (2.2%, 25 untreated embryos out of 1127 embryos in total) in embryos past the stage of neural tube closure. In the present experiments we obtained 22 gut-only situs inversus embryos having an inverted gut and a normal heart. In contrast, such embryos were not observed among the 1127 untreated embryos. An adrenergic signal mediated by an increase in intracellular free calcium may be involved in the asymmetrical visceral morphogenesis of Xenopus embryos.

Adrenergic alpha-Agonists↗
PubMed1974

Coexistence of several putative neurotransmitters in single identified neurons of Aplysia.

By sensitive enzymatic micromethods several putative neurotransmitters were measured in four identifiable neurons of Aplysia californica (R-2, R-14, L-11, and C-1). Serotonin was found in all of these neurons, and octopamine in all but C-1. Acetylcholine has been previously reported to be present in R-2 and L-11. The catecholamines, norepinephrine and dopamine, were not detected in the four cells examined. The possible biological consequence of the presence of several putative transmitters in single identifiable neurons is discussed.

Animals↗
PubMed1993

Cocaine as a naturally occurring insecticide.

Although cocaine has a fascinating and complex medicinal history in man, its natural function in plants is unknown. The present studies demonstrate that cocaine exerts insecticidal effects at concentrations which occur naturally in coca leaves. Unlike its known action on dopamine reuptake in mammals, cocaine's pesticidal effects are shown to result from a potentiation of insect octopaminergic neurotransmission. Amine-reuptake blockers of other structural classes also exert pesticidal activity with a rank order of potency distinct from that known to affect vertebrate amine transporters. These findings suggest that cocaine functions in plants as a natural insecticide and that octopamine transporters may be useful sites for targeting pesticides with selectivity toward invertebrates.

Animals↗
PubMed1997

Conserved and sexually dimorphic behavioral responses to biogenic amines in decapitated Drosophila.

A preparation of decapitated Drosophila melanogaster has been used for direct application of drugs to the nerve cord. Serotonin, dopamine, and octopamine stimulate locomotion and grooming, showing distinguishable effects that often are potentiated by addition of the vertebrate monoamine oxidase-inhibitor hydrazaline. Many of the hydrazaline-induced effects are sexually dimorphic, with males showing greater responses than females. Behaviors similar to those induced by dopamine can be induced by application of the vertebrate dopamine D2-like receptor agonist quinpirole, whose effects are also sexually dimorphic. In contrast, vertebrate D2-like and D1-like dopamine antagonists result in akinesic states, and D1-like agonists selectively stimulate grooming. These data indicate that Drosophila nerve cord amine receptors are coupled to reflexive behaviors similar to those stimulated by brain dopamine receptors in vertebrates.

Animals↗
PubMed1999

Cloning and expression of a potato cDNA encoding hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase.

Hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase (THT; EC 2.3.1.110) catalyzes the transfer of hydroxycinnamic acids from the respective CoA esters to tyramine and other amines in the formation of N-(hydroxycinnamoyl)amines. Expression of THT is induced by Phytophthora infestans, the causative agent of late blight disease in potato. The amino acid sequences of nine endopeptidase LysC-liberated peptides from purified potato THT were determined. Using degenerate primers, a THT-specific fragment was obtained by reverse transcription-polymerase chain reaction, and THT cDNA clones were isolated from a library constructed from RNA of elicitor-treated potato cells. The open reading frame encoding a protein of 248 amino acids was expressed in Escherichia coli. Recombinant THT exhibited a broad substrate specificity, similar to that of native potato THT, accepting cinnamoyl-, 4-coumaroyl-, caffeoyl-, feruloyl- and sinapoyl-CoA as acyl donors and tyramine, octopamine, and noradrenalin as acceptors tested. Elicitor-induced THT transcript accumulation in cultured potato cells peaked 5 h after initiation of treatment, whereas enzyme activity was highest from 5 to 30 h after elicitation. In soil-grown potato plants, THT mRNA was most abundant in roots. Genomic Southern analyses indicate that, in potato, THT is encoded by a multigene family.

Acyltransferases↗
PubMed2000

Quantitative structure-activity studies of octopaminergic agonists and antagonists against Locusta migratoria using similarity indexes.

The quantitative structure-activity relationship of 39 octopamine (OA) agonists and 12 antagonists against the thoracic nerve cord of the migratory locust, Locusta migratoria L. was analyzed using atom based rigid fit method or flexible fitting offered by PowerFit 1.0 from MicroSimulation. For OA agonists, the more similar to reference compound NC (24) the structure of test compound, the higher the activity, whereas for OA antagonists it was not the case. Antagonists may not interact with the same part of the membrane with which the agonists interact. Taken the part of the membrane with which the agonist interacts as the true receptor, the antagonist may well interact with an area surrounding the receptor including the ionophore.

Animals↗
PubMed1974

Biogenic amines in cultured neuroblastoma and astrocytoma cells.

The presence of biogenic amines in cultured cells of mouse neuroblastoma C-1300 (clone NB-2a) was suggested by fluorescence-microscope histochemistry. Incubation in media containing L-[(14)C]tyrosine and L-[(14)C]tryptophan for 24 h, followed by high-voltage electrophoresis, radiochromatogram scanning, and scintillation counting, confirmed the presence of [(14)C]dopamine, [(14)C]norepinephrine, [(14)C]epinephrine, [(14)C]serotonin, [(14)C]tyramine, and [(14)C]octopamine. Dopamine, norepinephrine, epinephrine, and serotonin were demonstrated spectrophotofluorometrically in concentrations, expressed as micrograms amine per milligram protein, of 1.19, 0.027, 0.038, and 0.148, respectively, for cells in a stationary growth phase. Fluorescence-microscope histochemistry also suggested the presence of biogenic amines in cultured astrocytoma cells (cell line C6). Spectrophotofluorometric assay of cells in a stationary growth phase demonstrated intracellular dopamine, norepinephrine, epinephrine, and serotonin in concentrations significantly lower than those of neuroblastoma cells.

Animals↗
PubMed2001

Quantitative trait loci for the monoamine-related traits heart rate and headless behavior in Drosophila melanogaster.

Drosophila melanogaster appears to be well suited as a model organism for quantitative pharmacogenetic analysis. A genome-wide deficiency screen for haploinsufficient effects on prepupal heart rate identified nine regions of the genome that significantly reduce (five deficiencies) or increase (four deficiencies) heart rate across a range of genetic backgrounds. Candidate genes include several neurotransmitter receptor loci, particularly monoamine receptors, consistent with results of prior pharmacological manipulations of heart rate, as well as genes associated with paralytic phenotypes. Significant genetic variation is also shown to exist for a suite of four autonomic behaviors that are exhibited spontaneously upon decapitation, namely, grooming, grasping, righting, and quivering. Overall activity levels are increased by application of particular concentrations of the drugs octopamine and nicotine, but due to high environmental variance both within and among replicate vials, the significance of genetic variation among wild-type lines for response to the drugs is difficult to establish. An interval mapping design was also used to map two or three QTL for each behavioral trait in a set of recombinant inbred lines derived from the laboratory stocks Oregon-R and 2b.

Animals↗
PubMed2001

Cloning and characterization of a hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase induced in response to UV-C and wounding from Capsicum annuum.

Hydroxycinnamoyl-CoA : tyramine N-(hydroxycinnamoyl) transferase (THT) is a pivotal enzyme in the synthesis of N-(hydroxycinnamoyl)-amines, which are associated with cell wall fortification in plants. The cDNA encoding THT was cloned from the leaves of UV-C treated Capsicum annuum (hot pepper) using a differential screening strategy. The predicted protein encoded by the THT cDNA is 250 amino acids in length and has a relative molecular mass of 28,221. The protein sequence derived from the cDNA shares 76% and 67% identity with the potato and tobacco THT protein sequences, respectively. The recombinant pepper THT enzyme was purified using a bacterial overexpression system. The purified enzyme has a broad substrate specificity including acyl donors such as cinnamoyl-, sinapoyl-, feruloyl-, caffeoyl-, and 4-coumaroyl-CoA and acceptors such as tyramine and octopamine. In UV-C treated plants, the THT mRNA was strongly induced in leaves, and the elevated level of expression was stable for up to 36 h. THT mRNA also increased in leaves that were detached from the plant but not treated with UV-C. THT expression was measured in different plant tissues, and was constitutive at a similar level in leaf, root, stem, flower and fruit. Induction of THT mRNA was correlated with an increase in THT protein.

Acyltransferases↗
PubMed1982

Plasma levels of false neurotransmitters across the brain in portal-systemic encephalopathy.

Arterial and internal jugular venous levels of false neurotransmitters (FNTs: octopamine, OCT, and phenylethanolamine, PEA), aromatic and branched-chain amino acids, glutamine, ammonia, and pH were measured in patients with portal-systemic encephalopathy (PSE) and in appropriate controls to define the role of these parameters in the pathogenesis of hepatic coma. The typical plasma patterns reported in the literature were observed: hyperammonaemia (59 +/- 8 mumol/l v. controls 30 +/- 4, P less than 0.005), elevated OCT (19 +/- 3 nmol/l v. 6 +/- 1, P less than 0.001) and PEA (64 +/- 8 nmol/l v. 27 +/-3, P less than 0.001), high ratio of aromatic to branched-chain amino acids (0.92 +/- 0.12 v. 0.32 +/- 0.04, P less than 0.005), and variable glutamine levels 216-734 mumol/l). No consistent net flux into or out of the brain could be demonstrated for any of these substances. The degree of encephalopathy correlated with the level of respiratory alkalosis (r=0.325, P less than 0.05) which, in turn, correlated with the degree of elevation of plasma OCT (r=0.439, P less than 0.05) and PEA (r=0.489, P less than 0.05) as well as with the excess of glutamine efflux from the brain (r=0.927, P less than 0.05). These findings support current views that hyperammonaemia, plasma amino acid imbalance, and elevated production of FNTs are interrelated disturbances which contribute to the pathogenesis of PSE. In addition, the data suggest that alkalosis accentuates the altered metabolism of these substances within the brain.

2-Hydroxyphenethylamine↗
PubMed2005

Participation of octopaminergic reward system and dopaminergic punishment system in insect olfactory learning revealed by pharmacological study.

Biogenic amines play major roles in the regulation of behavior in vertebrates and invertebrates. Previous studies in honey bees and fruit-flies Drosophila suggested that octopamine (OA, invertebrate counterpart of noradrenaline) and dopamine (DA) participate in appetitive olfactory conditioning with sucrose reward and aversive olfactory conditioning with electric shock punishment, respectively. In order to determine whether the effects of the two chatecholamines on electric shock and sugar learning can be generalized to other kinds of appetitive and aversive reinforcers, we studied the effects of OA and DA receptor antagonists on appetitive olfactory learning with water reward, and aversive olfactory learning with saline punishment in the cricket Gryllus bimaculatus. Crickets injected with epinastine or mianserin, OA receptor antagonists, into the hemolymph exhibited an impairment of appetitive learning with water reward, while aversive learning with saline punishment remained intact. In contrast, fluphenazine, chlorpromazine or spiperone, DA receptor antagonists, impaired aversive learning without affecting appetitive learning. This finding, combined with findings in previous studies, suggests that the octopaminergic reward system and dopaminergic punishment system participate in insect olfactory learning with various appetitive and aversive reinforcements.

Animals↗
PubMed2006

Roles of octopaminergic and dopaminergic neurons in mediating reward and punishment signals in insect visual learning.

Insects, like vertebrates, have considerable ability to associate visual, olfactory or other sensory signals with reward or punishment. Previous studies in crickets, honey bees and fruit-flies have suggested that octopamine (OA, invertebrate counterpart of noradrenaline) and dopamine (DA) mediate various kinds of reward and punishment signals in olfactory learning. However, whether the roles of OA and DA in mediating positive and negative reinforcing signals can be generalized to learning of sensory signals other than odors remained unknown. Here we first established a visual learning paradigm in which to associate a visual pattern with water reward or saline punishment for crickets and found that memory after aversive conditioning decayed much faster than that after appetitive conditioning. Then, we pharmacologically studied the roles of OA and DA in appetitive and aversive forms of visual learning. Crickets injected with epinastine or mianserin, OA receptor antagonists, into the hemolymph exhibited a complete impairment of appetitive learning to associate a visual pattern with water reward, but aversive learning with saline punishment was unaffected. By contrast, fluphenazine, chlorpromazine or spiperone, DA receptor antagonists, completely impaired aversive learning without affecting appetitive learning. The results demonstrate that OA and DA participate in reward and punishment conditioning in visual learning. This finding, together with results of previous studies on the roles of OA and DA in olfactory learning, suggests ubiquitous roles of the octopaminergic reward system and dopaminergic punishment system in insect learning.

Animals↗
PubMed1983

Respective roles of ammonia, amino acids, and medium-sized molecules in the pathogenesis of experimentally induced acute hepatic encephalopathy.

Ammonia, amino acids (AA), and middle molecules (MM) have been implicated in the pathogenesis of experimentally induced acute hepatic coma in the pig. Hemodialysis (HD) using either a low- (Cuprophan = CU) or a high-permeability (polyacrylonitrile = AN 69) membrane has demonstrated the role of MM. Selective hemodialysis (SHD) of AA or NH3 and MM was performed by adding either NH3 (group I) or AA (group II) to the dialysate during AN 69 HD; for MM, SHD only was performed by adding NH3 and AA to the dialysate (group III). In group I the brain levels of tyrosine were similar to those in undialyzed animals with decreased striatal dopamine and decreased norepinephrine in the midbrain only. Brain tryptophan was higher than normal, but brain levels of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid (5-HT, 5-HIAA) were within normal limits. In group II, despite an efficient NH3 clearance, brain NH3 levels were as high as in group I and did not correlate with plasma levels. Brain tyrosine (despite tyrosine overload of the dialysate) was lower than in group I; striatal dopamine decreased (but to a lesser extent than in group I), and norepinephrine was normal. Brain tryptophan was higher than normal, with an increase in brain 5-HT and 5-HIAA. In group III, results were similar to group I, except for a limited increase of 5-HT in the pons. Brain octopamine levels increased only in undialyzed and CU-HD animals, demonstrating a specific relation with MM. These experiments demonstrate the interrelationship between NH3 and neutral AA with regard to passage through the blood-brain barrier and to intracerebral metabolism.

Amino Acids↗
PubMed1992

Determination of acidic metabolites of biogenic amines in human aqueous humour by gas chromatography--negative ion chemical ionisation mass spectrometry.

The concentrations of acidic metabolites derived from the biogenic amines o-, m-, and p-tyramines (o-, m-, and p-hydroxyphenylacetic acids), p-octopamine/p-synephrine (p-hydroxymandelic acid), and dopamine (homovanillic acid and 3,4-dihydroxyphenylacetic acid) were measured in human aqueous humour obtained from patients undergoing elective surgery for cataract removal or for trabeculectomy as a treatment for chronic open-angle glaucoma. There were no clear differences in the pattern of metabolism of neurotransmitters between the two groups. An unexpected finding was that the o-tyramine metabolite, o-hydroxyphenylacetic acid, was present in aqueous humour.

Acids↗
PubMed1968

The effects of intracerebroventricularly administered noradnamine and other sympathomimetic amines upon leptazol convulsions in mice.

1. The influence of some intracerebroventricularly administered sympathomimetic amines on leptazol-induced convulsions has been investigated.2. Noradnamine and high doses of dopamine proved to be anticonvulsant and also antagonized the facilitative effects of reserpine.3. Noradrenaline and octopamine also antagonized reserpine-induced facilitation but were without effect on leptazol alone; by contrast tyramine and small doses of dopamine lowered the threshold for leptazol convulsions.4. A possible interpretation of these results is presented.

Animals↗