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At least 811 records · Page 45Linked to original sources
PubMed1980

Synaptosomal uptake and release of dopamine and 5-hydroxy-tryptamine in the nucleus accumbens in vitro following in vivo administration of lysergic acid diethylamide in rats.

The uptake and the depolarisation-induced release of dopamine (DA) and serotonin (5-HT) were investigated after systemic application of LSD on synaptosomes of the nucleus accumbens of rats. For the release experiments synaptosomes were prelabelled with [14C]-DA and [3H]-5-HT, respectively, and superfused with physiological and potassium-enriched (50 mM) solutions. Low doses of LSD (0.1 and 0.5 mg/kg i. p.) induced a dose-dependent inhibition of the DA-release and an increase of the DA-uptake, respectively. LSD inhibited both the release and the uptake of 5-HT significantly. The results are discussed with respect to a reliable characterization of the in vivo induced effects of LSD on the isolated synaptosomes.

Animals↗
PubMed1995

Effect of membrane surface potential on the uptake and the inhibition of cationic compounds in rat intestinal brush-border membrane vesicles and liposomes.

The effect of membrane surface potential on the uptake of tryptamine, an organic cation, by rat intestinal brush-border membrane vesicles was investigated. In the presence of an inside-negative K(+)-diffusion potential, the manner of initial uptake of tryptamine appeared to be pH-dependent and the uptake in the acidic medium was lower than that in the neutral medium. Changes in surface potential of brush-border membrane vesicles were monitored using 8-anilino-1-naphthalenesulfonic acid (ANS) and the results suggested that the membrane surface potential (negative charge on the membrane surface) decreased in the acidic medium. A good correlation was observed between the K(+)-diffusion potential-dependent uptake of tryptamine and membrane surface potential monitored by ANS at various pH levels. The uptake of tryptamine by liposomes (large unilamellar vesicles), which contained various amounts of dipalmitoylphosphatidylserine (DPPS), was also examined. The uptake of tryptamine decreased with a decrease of DPPS content in the liposomes, and was correlated with the membrane surface potential monitored by ANS. Moreover, the effect of organic cations on the uptake of tryptamine by intestinal brush-border membrane vesicles was examined. The uptake of tryptamine was inhibited by tetracaine and imipramine. The inhibitory effect of these cations was well correlated with changes in the membrane surface potential in the presence of tetracaine or imipramine. These results suggest that the K(+)-diffusion potential-dependent uptake of tryptamine by intestinal brush-border membrane vesicles is affected by membrane surface potential, and the inhibition of tryptamine uptake originates in changes in the membrane surface potential caused by the organic cations.

Animals↗
PubMed1984

Monoamine oxidase inhibitors in South American hallucinogenic plants Part 2: Constituents of orally-active Myristicaceous hallucinogens.

Alkaloid constituents in Myristicaceous bark and leaf samples and in purportedly hallucinogenic preparations derived from Myristicaceous sources were qualitatively and quantitatively analyzed using TLC, GC, alkaloid precipitation tests and GC/MS. Fourteen of the 27 bark and leaf samples analyzed contained detectable amounts of alkaloids. The major bases were N,N-dimethyltryptamine (DMT) and/or 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT); much smaller amounts of tryptamine and/or N-methyl-tryptamine (NMT) were also usually present. beta-Carbolines were not detected in the bark or leaf samples. Considerable variation in alkaloid profiles was found, extending to different collections of the same species. Fourteen of the 20 Virola samples contained alkaloids; none of the 6 Iryanthera species had detectable alkaloids. Osteophloem platyspermum contained an indolic base, identified as N-methyl-tryptophan methyl ester. Seven samples of an orally-ingested drug made from Virola spp. were analyzed. All except one contained substantial amounts of tryptamines; the types and proportions of tryptamines present varied greatly between samples. Samples of Yanomama snuff including various admixtures were analyzed and all components but one contained tryptamines. The drug samples having the highest concentrations of alkaloids contained 15-20 mg/g dry wt while the Myristicaceous bark and leaf samples had much lower concentrations ranging from 0.04 to 0.25 mg/g dry wt. beta-Carbolines were detected as trace constituents in only two of the Myristicaceous drug samples. Four Myristicaceous paste samples were bioassayed in self-experiments. Two of the samples were devoid of detectable hallucinogenic or physiological activity, while some degree of oral activity was detected in two other samples. The activity of a number of tryptamine derivatives as monoamine oxidase inhibitors (MAOI) was investigated using an in vitro enzyme assay. Activity was measured using single compounds and mixtures of compounds and the results were compared to the activity of samples of orally-ingested Myristicaceous pastes. Tryptamine derivatives had significantly less MAOI activity than the activity of beta-carboline derivatives measured in a previous study. Some structural correlations for MAOI activity were found for the tryptamine derivatives. Samples of orally-ingested Myristicaceous pastes were assayed for MAOI activity. The inhibition elicited by the paste samples was closely matched by mixtures of tryptamine standards having comparable proportions and concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Oral↗
PubMed1985

Pharmacology of harmalan (1-methyl-3,4-dihydro-beta-carboline).

Harmalan is presumably formed in vivo as an intermediate product of the biosynthesis of harman as well as tetrahydroharman. The pharmacological effects of harmalan as well as its affinity towards benzodiazepine, 5-HT2 and tryptamine binding sites were investigated in the present study. Harmalan induced clonic convulsions which were antagonized by diazepam. Receptor binding experiments as well as combined treatments with antagonists point to an interaction which involves neither benzodiazepine nor 5HT2 receptor sites but rather tryptamine binding sites. Good agreement was found between the potency of harmalan to increase spontaneous motor activity and the affinity to the tryptamine binding sites when compared with the effects of tryptamine in both tests. In the light-dark-chamber test for predicting anxiolytic effects of drugs, harmalan elicited opposite effects to diazepam. The results of combined treatment also suggested an interaction of both compounds not involving benzodiazepine receptors. Tryptamine binding sites seemed to play no role since the amine was inactive under these conditions. Thus, harmalan induces several tryptamine agonistic effects and others not involving tryptamine binding sites.

Animals↗
PubMed2005

Expression of the Arabidopsis feedback-insensitive anthranilate synthase holoenzyme and tryptophan decarboxylase genes in Catharanthus roseus hairy roots.

In plants, the indole pathway provides precursors for a variety of secondary metabolites. In Catharanthus roseus, a decarboxylated derivative of tryptophan, tryptamine, is a building block for the biosynthesis of terpenoid indole alkaloids. Previously, we manipulated the indole pathway by introducing an Arabidopsis feedback-insensitive anthranilate synthase (AS) alpha subunit (trp5) cDNA and C. roseus tryptophan decarboxylase gene (TDC) under the control of a glucocorticoid-inducible promoter into C. roseus hairy roots [Hughes, E.H., Hong, S.-B., Gibson, S.I., Shanks, J.V., San, K.-Y. 2004a. Expression of a feedback-resistant anthranilate synthase in Catharanthus roseus hairy roots provides evidence for tight regulation of terpenoid indole alkaloid levels. Biotechnol. Bioeng. 86, 718-727; Hughes, E.H., Hong, S.-B., Gibson, S.I., Shanks, J.V., San, K.-Y. 2004b. Metabolic engineering of the indole pathway in Catharanthus roseus hairy roots and increased accumulation of tryptamine and serpentine. Metabol. Eng. 6, 268-276]. Inducible expression of either or both transgenes did not lead to significant increases in overall alkaloid levels despite the considerable accumulation of tryptophan and tryptamine. In an attempt to more successfully engineer the indole pathway, a wild type Arabidopsis ASbeta subunit (ASB1) cDNA was constitutively expressed along with the inducible expression of trp5 and TDC in C. roseus hairy roots. Transgenic hairy roots expressing both trp5 and ASB1 show a significantly greater resistance to feedback inhibition of AS activity by tryptophan than plants expressing only trp5. In fact, a 4.5-fold higher concentration of tryptophan is required to achieve 50% inhibition of AS activity in plants overexpressing both genes than in plants expressing only trp5. In addition, upon a 3 day induction during the exponential phase, a trp5:ASB1 hairy root line produced 1.8 times more tryptophan (specific yield ca. 3.0 mg g(-1) dry weight) than the trp5 hairy root line. Concurrently, tryptamine levels increase up to 9-fold in the induced trp5:ASB1 line (specific yield ca. 1.9 mg g(-1) dry weight) as compared with only a 4-fold tryptamine increase in the induced trp5 line (specific yield ca. 0.3 mg g(-1) dry weight). However, endogenous TDC activities of both trp5:ASB1 and trp5 lines remain unchanged irrespective of induction. When TDC is ectopically expressed together with trp5 and ASB1, the induced trp5:ASB1:TDC hairy root line accumulates tryptamine up to 14-fold higher than the uninduced line. In parallel with the remarkable accumulation of tryptamine upon induction, alkaloid accumulation levels were significantly changed depending on the duration and dosage of induction.

Anthranilate Synthase↗
PubMed2000

Comparison of neurochemical effects of the monoamine oxidase inhibitors phenelzine, moclobemide and brofaromine in the rat after short- and long-term administration.

BACKGROUND: Chronic administration of several irreversible monoamine oxidase (MAO) inhibitors induces a down-regulation of tryptamine and 5-hydroxytryptamine(2) receptors in rat brain, but there is a paucity of information available on the effects of reversible MAO-A inhibitors on these receptors. METHODS: Acute and chronic experiments were conducted in rats and the effects of the irreversible monoamine oxidase inhibitor, phenelzine and the reversible MAO type-A inhibitors, moclobemide and brofaromine, on tryptamine and 5-hydroxytryptamine(2) receptors were analysed using radioligand binding techniques. In addition, activities of MAO-A and -B were determined radiochemically and brain and/or urine levels of tryptamine, 5-hydroxytryptamine, 3-methoxy-4-hydroxyphenylglycol (MHPG), beta-phenylethylamine, brofaromine and moclobemide were determined by chromatographic procedures. RESULTS: After 30 days of administration, moclobemide and brofaromine selectively inhibited brain MAO-A activity and phenelzine inhibited MAO-A and -B to equal extents. All three drugs caused a significant down-regulation of tryptamine receptors, whereas only phenelzine significantly down-regulated 5-hydroxytryptamine(2) receptors. In a comparison of phenelzine and brofaromine, both caused marked elevations of urinary tryptamine and decreases of urinary MHPG levels, while only phenelzine increased beta-phenylethylamine levels. After 14 days of administration, phenelzine, but not moclobemide or brofaromine, significantly increased levels of tryptamine in brain; all three drugs significantly increased 5-HT levels. LIMITATIONS: 24-h urine samples were not collected for moclobemide-treated animals and brain levels of tryptamine were not measured after 30-day administration. CONCLUSIONS: These studies revealed marked neurochemical differences among phenelzine, moclobemide and brofaromine which could contribute to their actions in the clinical setting.

Animals↗
PubMed1976

Preliminary investigations of the metabolism and pharmacological activity of beta-hydroxytryptamines in mammals.

beta-Hydroxytryptamine and beta-hydroxy-5-hydroxytryptamine were incubated with rat liver slices and oxidative deamination was established as the main route of metabolism: in both instances the corresponding indole-3-glycollic acids and indole-3-ethane diols were the major metabolites. However, the rates of deamination of beta-hydroxylated tryptamines, as measured manometrically, were found to be much slower than those of tryptamines nonhydroxylated in the side chain. The pharmacological activities of beta-hydroxylated tryptamines were tested in guinea-pigs on resistance of respiratory pathways, spontaneous respiration, electrocardiogram, blood pressure and isolated ileum, using tryptamine and 5-HT as reference substances. The effects of tryptamines hydroxylated in the side chain were in general similar to those of corresponding tryptamines but of much lower intensities; only in increasing the blood pressure was beta-hydroxytryptamine as active as tryptamine. The different reactions of these two groups of substances in the presence of some antagonists indicate that the receptors are probably not the same.

Animals↗