piperidines and tryptamine

Brofaromine, a selective and reversible inhibitor of monoamine oxidase-A (MAO-A) was given to 19 women while 17 received placebo for 8 weeks. All met DSM III-R criteria for bulimia nervosa, a psychiatric disorder in which uncontrolled overeating episodes are accompanied by purging activities and extreme concerns about body shape and weight. The following indices were measured: plasma and urinary phenylacetic acid (PAA), homovanillic acid (HVA), vanillylmandellic acid (VMA); plasma tryptamine (T), beta phenylethylamine (PE), and 5-hydroxyindoleacetic acid (5-HIAA) and urinary 6-sulphatoxymelatonin (aMT6s). PE levels remained the same but T showed a trend toward elevation over time. Twenty-four hour levels of urinary aMT6s in BN patients were higher at week 4 when compared to baseline and week 8. There was a significant reduction in plasma VMA and HVA over time during treatment with brofaromine and both plasma HVA and VMA were significantly lower for the brofaromine group compared to placebo at week 4. Plasma 5-HIAA was significantly higher for the brofaromine group after 8 weeks when compared to placebo. Urinary VMA decreased significantly from baseline to week 4 with a partial elevation at 8 weeks. Urinary VMA was also significantly lower in patients on brofaromine at week 4. This study verifies that brofaromine complies with predicted MAO-A inhibiting patterns in a clinical population.

Topics: Adolescent; Adult; Biogenic Amines; Bulimia; Female; Homovanillic Acid; Humans; Hydrogen-Ion Concentration; Hydroxyindoleacetic Acid; Melatonin; Monoamine Oxidase Inhibitors; Piperidines; Tryptamines; Vanilmandelic Acid

The present study compared the extent and duration of MAO inhibition by the selective and reversible MAO-A inhibitor brofaromine with the selective and irreversible MAO-A inhibitor clorgyline using amine pressor tests and excretion of urinary amine metabolites (MHPG, tryptamine). The pharmacological characterization of clorgyline as an irreversible and brofaromine as a reversible MAO-A inhibitor in clinically effective doses was confirmed in humans.

Topics: Administration, Oral; Adult; Blood Pressure; Clorgyline; Cross-Over Studies; Dose-Response Relationship, Drug; Drug Synergism; Female; Humans; Hypertension; Infusions, Intravenous; Male; Methoxyhydroxyphenylglycol; Monoamine Oxidase; Norepinephrine; Piperidines; Reference Values; Tryptamines; Tyramine

The effects of brofaromine, clorgyline (reversible and irreversible type A MAO inhibitors, respectively) and tranylcypromine (non-selective MAO inhibitor) on rat striatal levels of phenylethylamine, tryptamine, m-tyramine and p-tyramine were determined. Brofaromine and clorgyline increased m- and p-tyramine levels, but not phenylethylamine levels. Brofaromine given at a dose of 100 mg/kg did increase tryptamine levels. Tranylcypromine increased the levels of all four amines greatly. The effects of chronic treatment with brofaromine on amine levels were not different from those following acute treatment. By contrast, chronic treatment with clorgyline caused greater increases in striatal m- and p-tyramine levels than did acute clorgyline. These data show that changes in the rat striatal levels of m-tyramine and p-tyramine may be used as in vivo indicators of the selectivity and reversiblity of inhibition of type A MAO, while tryptamine levels reflect non-selective inhibition of both types of MAO.

Topics: Animals; Biogenic Amines; Clorgyline; Corpus Striatum; Dose-Response Relationship, Drug; Drug Administration Schedule; Kinetics; Male; Monoamine Oxidase Inhibitors; Phenethylamines; Piperidines; Rats; Rats, Inbred Strains; Tranylcypromine; Tryptamines; Tyramine

The functional significance of the interaction between serotonergic and dopaminergic neurotransmission is still uncertain. To document this interaction further, specific behavioral responses of rats to tryptamine and apomorphine were studied. The sequential injection of these agonists, at time intervals with minimal direct behavioral interference, was used to observe response changes with respect to a single challenge. The antagonists haloperidol, ritanserin and risperidone, with known actions on serotonin-S2 (5-HT2) and dopamine-D2 (D2) receptors were used to evaluate effective antagonism of single and sequential challenges. When tryptamine was preceded by an apomorphine challenge the effective doses of the 5-HT2 antagonists ritanserin and risperidone for 50% inhibition of the seizures increased by a factor of 2.5. The dose-response curve of haloperidol remained virtually unchanged, apparently because of the potent dopamine-D2 antagonism associated with these doses which may block the potentiating effect of apomorphine. When apomorphine was preceded by a tryptamine challenge, the total agitation score of the control animals increased by 59% on the average. Haloperidol was equally effective against the enhanced as against the unenhanced apomorphine response. Ritanserin reduced agitation only by the part corresponding to the tryptamine enhancement. Risperidone's activity against the enhanced agitation started at very low doses and was complete at a dose still about 2.5 times lower than that required against the single apomorphine challenge. Mutual enhancement of tryptamine and apomorphine appears to occur even at a time when the behavioral effects of the first agonist are no longer manifest. The enhanced agitation remains largely dopamine-D2-specific and the enhanced seizures serotonin 5-HT2-specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antipsychotic Agents; Apomorphine; Dopamine; Dose-Response Relationship, Drug; Drug Interactions; Haloperidol; Injections, Intravenous; Isoxazoles; Male; Piperidines; Rats; Rats, Inbred Strains; Risperidone; Ritanserin; Seizures; Serotonin; Serotonin Antagonists; Synaptic Transmission; Tryptamines

The two monoamine oxidase (MAO) inhibitors phenelzine and brofaromine given for 2 to 3 weeks were compared in six volunteers. Blood pressure sensitivity to intravenous tyramine increased 2.6-fold during phenelzine (60 mg/day) and 4.8-fold during brofaromine, whereas sensitivity to oral tyramine increased more during phenelzine (15.7-fold vs 8.5-fold). After withdrawal of phenelzine, pressor sensitivity to oral tyramine returned to control values within 2 and for more than 8 weeks. Relative bioavailability of conjugated tyramine was elevated sixfold by brofaromine and 11.6-fold by phenelzine. Urinary elimination of tryptamine increased during phenelzine and brofaromine to 12.7-fold and threefold, respectively. 3-Methoxy-4-hydroxyphenylglycol (MHPG) and 3-methoxy-4-hydroxymandelic acid (VMA) excretion decreased during brofaromine significantly by 72% and 49%, respectively. The nonsignificant decrease of MHPG excretion and the increase of intravenous tyramine pressor sensitivity caused by phenelzine are significantly related. The data suggest that the selective reversible MAO-A inhibitor brofaromine has a larger therapeutic safety than phenelzine.

Topics: Adult; Biological Availability; Blood Pressure; Heart Rate; Humans; Male; Methoxyhydroxyphenylglycol; Monoamine Oxidase Inhibitors; Phenelzine; Piperidines; Tryptamines; Tyramine; Vanilmandelic Acid

The behavioural effects of intravenously administered tryptamine were examined in mice. Tryptamine in a dose greater than 15 mg/kg induced distinct head-weaving and hindlimb abduction. These behavioural syndromes appeared immediately after the injection and disappeared within 3 min. The changes in time course of the behaviour induced by tryptamine were consistent with those of the levels of tryptamine in the brain. Pretreatment with p-chlorophenylalanine, a depleter of 5-hydroxytryptamine (5-HT), failed to alter the effects of tryptamine on head-weaving or hindlimb abduction but did result in head-twitches which were never seen after tryptamine alone. Metergoline strongly antagonized the behavior induced by tryptamine. Pirenperone and haloperidol inhibited the behavioural syndrome, antagonizing the head-weaving in particular. alpha-Methyl-p-tyrosine, a depleter of dopamine, reduced the head-weaving without affecting the hindlimb abduction. These results indicate that the 5-HT syndrome induced by intravenous administration of tryptamine is due to the direct effect of tryptamine on the 5-HT receptor. Tryptamine-induced behaviour, especially head-weaving, seems to be linked with dopaminergic neurones.

Topics: Animals; Behavior, Animal; Brain; Dopamine; Haloperidol; Indoleacetic Acids; Metergoline; Mice; Piperidines; Receptors, Serotonin; Serotonin; Tryptamines

Rats were chronically treated with setoperone, a mixed serotonin and dopamine antagonist. Alterations in serotonin-S2 and dopamine-D2 receptors in the brain and changes in behavioural responses to tryptamine and apomorphine were studied along with duration of treatment and drug withdrawal. As with neuroleptics, behavioural supersensitivity to apomorphine and increase in the number of striatal dopamine-D2 receptor sites were apparent after 2 days setoperone treatment, both effects were maximal with 14 days treatment and were maintained over more than 20 days drug withdrawal. In contrast to the changes in the dopaminergic system, the rats showed a decreased response to tryptamine and serotonin-S2 receptor sites in the frontal cortex were significantly reduced in numbers. Both effects developed in parallel over 14 days treatment and extinguished over 10 days drug withdrawal. KD-values of radioligand binding to dopamine-D2 and serotonin-S2 receptor sites were unchanged by the setoperone treatment. The concomitant development and extinction of the in vivo and in vitro effects suggests a causal relationship between them. Chronic treatment with a selective histamine-H1 antagonist (levocabastine) or the tranquilizer diazepam did not affect dopamine-D2 or serotonin-S2 receptor sites. These observations demonstrate that in contrast to the receptor regulation theory, serotonin-S2 receptors are down regulated following persistent receptor blockade. Implications for the clinical use of serotonin antagonists and possible molecular mechanisms involved in the receptor regulation have been discussed.

Topics: Animals; Apomorphine; Behavior, Animal; Corpus Striatum; Diazepam; Dopamine Antagonists; Frontal Lobe; Gene Expression Regulation; Ketanserin; Male; Models, Biological; Piperidines; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Serotonin; Serotonin Antagonists; Tryptamines

The ability of the putative serotonin2 (5-HT2) antagonist ketanserin, to alter serotonin (5-HT)-induced responses in cell firing was examined in the prefrontal cortex, the lateral geniculate nucleus and the dorsal raphe nucleus of the rat by microiontophoretic extracellular single unit recording techniques. In the prefrontal cortex, ketanserin failed to antagonize the inhibitory effects of 5-HT recorded in cerveau isolé or preparations anesthetized with chloral hydrate (pure excitatory responses to 5-HT were not observed in either of these preparations). Paradoxically, the inhibitory response produced by 5-HT (but not gamma-aminobutyric acid, tryptamine or norepinephrine) was potentiated, even in cells where ketanserin alone did not alter spontaneous firing rates. The systemic administration of ketanserin (5 mg/kg, i.p.) had effects similar to those observed in the microiontophoretic experiments in the prefrontal cortex. In the dorsal raphe nucleus of animals anesthetized with chloral hydrate, ketanserin neither attenuated nor potentiated the inhibition of serotonergic neurons by 5-HT. In the lateral geniculate nucleus, as in the prefrontal cortex, ketanserin potentiated rather than attenuated, the inhibitory effect of 5-HT. Ketanserin was found to attenuate the excitatory responses produced by norepinephrine, an alpha 1-adrenoceptor-mediated response, in the lateral geniculate nucleus. The observed potentiation by ketanserin of inhibitory responses to 5-HT but not those of gamma-aminobutyric acid, tryptamine or norepinephrine, recorded in the prefrontal cortex, may be consistent with the proposed interaction between ketanserin and a specific 5-HT2 binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Decerebrate State; Electrophysiology; Frontal Lobe; gamma-Aminobutyric Acid; Geniculate Bodies; Ketanserin; Male; Norepinephrine; Piperidines; Raphe Nuclei; Rats; Rats, Inbred Strains; Serotonin; Tryptamines

It has been suggested that tryptamine can stimulate specific receptors distinct from those for 5-hydroxytryptamine (5-HT). We have examined this possibility in the rat isolated caudal artery, paying particular attention to the involvement of monoamine oxidase metabolism and alpha-adrenoceptors, two factors that can complicate the quantification of antagonist potencies at 5-HT receptors. 5-HT and tryptamine were agonists over the concentration-ranges 3.0 X 10(-8) - 3.0 X 10(-5) mol l-1 and 1.0 X 10(-6) - 3.0 X 10(-4) mol l-1 respectively. The sensitivity of the caudal artery to tryptamine was increased by about 44 fold in the presence of iproniazid (5.0 X 10(-5) mol l-1) and about 17 fold in the presence of pargyline (1.0 X 10(-5) mol l-1), while responses to 5-HT and methoxamine were unaffected. In the absence of iproniazid, ketanserin and methysergide were potent antagonists of responses to 5-HT with pA2 values of 9.08 and 9.11 and slopes of the Schild regressions of 1.15 and 1.00 respectively. However, against tryptamine the antagonists were weaker such that pA2 values were similar to those against 5-HT but the slopes of the Schild regressions were 0.47 and 0.47. In the presence of iproniazid (or pargyline), the 5-HT antagonists were more potent against tryptamine such that the pA2 values and the slopes of the Schild regressions were not significantly different from those against 5-HT. Phentolamine was a weak antagonist of responses to both 5-HT and tryptamine in the presence of iproniazid. 5 The findings in this study suggest that the contractile action of tryptamine in rat caudal artery is mediated predominantly by the same receptor as 5-HT and that the differential inactivation of tryptamine by monoamine oxidase enzymes largely accounts for the different susceptibilities of 5-HT and tryptamine to the antagonists examined.

Topics: Animals; Arteries; In Vitro Techniques; Ketanserin; Male; Methysergide; Monoamine Oxidase Inhibitors; Phentolamine; Piperidines; Rats; Rats, Inbred Strains; Receptors, Serotonin; Serotonin; Tryptamines; Vasoconstriction

Calves were sensitized with horse plasma (H.P.), 0.2 ml/kg, i.v., and H.P. (0.2 ml/kg) in Freund's complete adjuvant, s.c. The latter injection was repeated 1 week later and the animals were killed 10 days after the second injection. Spirally cut strips of pulmonary artery and vein and the trachealis muscle from the sensitized calves contracted to 5-hydroxytryptamine (5-HT) and specific antigen (horse plasma). Antigen-induced contractions of the pulmonary smooth muscles were significantly blocked (P less than 0.05) by the 5-HT antagonists, methysergide and ketanserin. The trachea, however, appeared less sensitive to the antagonists than the pulmonary vessels. The results suggest that 5-HT participates in the pulmonary anaphylactic reactions of cattle and that ketanserin may be useful in suppressing bovine pulmonary hypersensitivities.

Topics: Anaphylaxis; Animals; Cattle; Horses; In Vitro Techniques; Ketanserin; Lung; Methysergide; Muscle Contraction; Muscle, Smooth; Piperidines; Pulmonary Artery; Pulmonary Veins; Serotonin Antagonists; Trachea; Tryptamines