[Isatin: possible role in functional interaction of natriuretic peptides and monoamines]

Isatin is an endogenous compound recently discovered in mammalian tissues and body fluids. It has a distinct distribution in rat brain, with a highest concentration, in the hippocampus, of 0.1 microgram/g. Its origin and metabolic pathways remain unclear. In vitro, isatin selectively inhibits monoamine oxidase (MAO) B (IC50 3-8 microM, Ki approximately 20 microM) and, more potently, atrial natriuretic peptide(ANP) binding (IC50, 0.4 microM). Convulsant doses of pentylene tetrazole result in increased isatin level in the brain. Small amounts of isatin are anxiogenic in rodent models, but higher doses cause sedation and possess anticonvulsant action. Isatin administration also increases monoamine levels in the brain and reduces daily urine output.

Brain-derived neurotrophic factor in human platelets

A sensitive, capture enzyme-linked immunosorbent assay (CELISA) has been applied to the accurate and reproducible measurement of brain-derived neurotrophic factor (BDNF) protein in normal human blood platelets, a mean concentration of 1.03 +/- 0.04 ng (SEM)/mg of platelet protein being observed. The method, which requires only 10 ml blood, is now suitable for the investigation of a variety of clinical disorders.

Dynamic breath-hold 3D gadolinium-enhanced MRI of intraarterial masses: findings in two patients

We describe the use of dynamic breath-hold gadolinium-enhanced 3D MRI for the evaluation of intraarterial masses and its potential use in differentiating thrombus from neoplasm. This rapid technique overcomes the flow artifacts that may obscure intraarterial masses on contrast-enhanced ECG-gated SE MR and can be performed on patients who otherwise cannot be ECG gated.

Metabolism of phenylethanolamines and 2-oxo-2-phenylethylamines in the rat

1. The metabolism of a series of phenylethanolamines and 2-oxo-2-phenylethylamines was examined in vivo in the rat. 2. The urinary excretion of the corresponding mandelic acids was, in general, considerably greater for 2-oxo-2-phenylethylamines than for the corresponding phenylethanolamines. Of the putative metabolites of the former class of compounds only phenylglyoxals yielded mandelic acids.

Effects of some anxiogenic agents on rat brain monoamine oxidase (MAO) A and B inhibitory (tribulin) activity

Anxiogenic agents, yohimbine, pentylenetetrazole (PTZ), quinine, bufotenine, flumazenil and isatin were administered (ip) to rats at doses known to induce anxiety in this species. All the drugs exhibited anxiogenic response on the elevated plus-maze and induced a parallel increase in endogenous brain monoamine oxidase (MAO) inhibitory (tribulin) activity. The intensity of the drug-induced anxiety was fairly well correlated with the magnitude of increase in the MAO A inhibitory component of tribulin but not so with its MAO B inhibitory component. Thus, in the doses used, the degree of anxiogenic activity was PTZ > yohimbine > bufotenine > quinine > isatin > flumazenil, in terms of % entries on the open arms of the maze, whereas the magnitude of endogenous MAO A inhibition was PTZ > yohimbine > bufotenine > quinine > flumazenil > isatin. The results indicate that the MAO A inhibitory component of tribulin, rather than its MAO B inhibitory component, may be responsible for the postulated function of tribulin as an endogenous marker of anxiety.

Isatin: a link between natriuretic peptides and monoamines?

Isatin is an endogenous indole with a distinctive distribution in brain and tissues. In the brain, the highest levels have been found in the hippocampus (0.1 microgram/g), and an immunocytochemical stain has shown specific localization within particular cells. In vitro, its most potent known actions are as an inhibitor of monoamine oxidase B (IC50 approximately 3 microM), and of atrial natriuretic peptide (ANP) receptor binding and ANP-induced guanylate cyclase (both with an IC50 approximately 0.4 microM). In vivo, isatin administration (10-200 mg/kg) causes an increase of monoamine neurotransmitter levels in the brain. Isatin is anxiogenic in animal models at doses of 10-20 mg/kg and sedative at higher doses. Its anxiogenic effects are unlikely to be due to inhibition of monoamine oxidase, but may possibly stem from interaction with the ANP system. Isatin may mediate a link between monoamines and the natriuretic peptide system, and its analogues may provide new pharmacological tools.

Anxiolytic activity of intraventricularly administered atrial natriuretic peptide in the rat

Rat atrial natriuretic peptide (ANP) was investigated for putative anxiolytic activity in rats, following intracerebroventricular (ICV) administration. ANP in doses of 200 and 500 ng/rat induced significant anxiolysis, comparable with that of lorazepam (0.5 mg/kg, i.p.) in a variety of anxiety models (open-field, elevated plus-maze, social interaction, and novelty-induced feeding suppression tests). Isatin, an endogenous anxiogenic indole, shown to be an antagonist of ANP in vitro, significantly inhibited the anxiolytic effect of ANP in the elevated plus-maze test in subanxiogenic doses. The anxiolytic action of ANP was unaffected by flumazenil, a benzodiazepine receptor antagonist. Conversely, the anxiolytic action of lorazepam was antagonized by flumazenil but not by isatin. The data indicate that ANP may function as an endogenous anxiomodulator, which may act in conjunction with isatin independently of benzodiazepine receptors. These results strengthen the evidence for links between physiological systems involved in anxiety and those in natriuresis.

Red wine-induced release of [14C]5-hydroxytryptamine from platelets of migraine patients and controls

Red wine-induced release of [14C]5-hydroxytryptamine (5HT) from platelets of red wine-sensitive migraine patients, migraine patients not sensitive to red wine and controls, was determined in vitro. No significant differences in platelet [14C]5HT release were found between any of the groups investigated.

Paracetamol (acetominophen) sulphoconjugation in man: no correlation with tyramine sulphoconjugation

There is considerable evidence that subjects vulnerable to endogenous depression excrete less tyramine sulphate after an oral dose of free tyramine than controls (the tyramine test). In this study, 26 psychiatric inpatients, exhibiting a wide range of responses to the test, and 10 normal controls were challenged with oral doses of paracetamol and tyramine on two separate occasions. Urinary output of paracetamol sulphate and paracetamol glucuronide in all subjects was monitored but there were no significant correlations with tyramine sulphate output. Thus, the output of these metabolites appears to be under complex control, and paracetamol cannot be substituted for tyramine in the "tyramine test". The basic deficit responsible for low values in the tyramine test is unlikely to stem from sulphate depletion or a generalised disturbance of the sulphation system, and remains obscure.

Somatostatin receptor imaging: predictive and prognostic considerations

Compared with other imaging modalities and clinical investigation, the 111In-pentetreotide scan identified additional metastatic disease sites in 12 carcinoid patients and 2 occult primaries, and influenced the therapeutic outcome in 36 patients [29 carcinoids, 2 atypical carcinoids, 3 cancers of unknown primaries (CUPs) and 2 medullary thyroid carcinomas (MCTs)]. No adverse reactions were noted. Somatostatin receptors were detected in 59/60 carcinoid patients, 3/4 atypical carcinoid patients, 0/2 MCT patients, and 0/3 cases of CUP. Somatostatin receptor presence is underestimated in some patients using standard hormonal response criteria rather than scintigraphy. 18 patients with metastatic carcinoids who underwent 111In-pentetreotide scanning were all somatostatin receptor positive. Their mean (+/- SE) 5-hydroxyindoleacetic acid (5-HIAA) suppression with octreotide therapy was -53% (+/- 6%). 8 patients had < 50% and 10 had > 50% 5-HIAA suppression (ranges: -4 to -47% and -58 to -94%, respectively). To investigate the effect of somatostatin analogues on survival, 90 consecutive cases of carcinoid syndrome patients treated during the somatostatin analogue era were reviewed. Survival according to primary site was 12.01, 18.29 and 6.05 years (overall median 12.01 years) for patients with foregut, midgut and unknown primaries, respectively. The difference from historical controls is substantial (67 vs. 18% 5-year survival), although our series is neither prospective nor randomised. The heterogeneity in patient and tumour response to somatostatin analogue therapy is discussed.

Tyramine conjugation deficit in migraine, tension-type headache, and depression

This study was designed to investigate tyramine sulfate conjugation in patients with migraine or tension-type headache, as defined by the newly introduced International Headache Society (IHS) criteria and to examine whether this relationship is mediated by major depression. A total of 62 subjects completed the study: 38 with migraine (22 with aura and 16 without aura), 12 with tension-type headache, and 12 controls. Patients with migraine had significantly lower urinary tyramine sulfate excretion following oral tyramine challenge than normal control. Tension-type headache was also associated with low tyramine conjugation, but only when comorbid with depression. Although mean tyramine sulfate output was lower among subjects with major depression within each of the subtypes of headache, no significant main effect emerged for depression or major subtype thereof. The lower tyramine sulfate excretion values among patients with both migraine and depression compared to those of migraine alone or depression alone in our data and those of others suggests that comorbid migraine with depression may represent a more severe form of migraine than migraine alone. The findings underscore the importance of comorbidity in clinical and epidemiological studies of migraine.

Rat brain monoamine oxidase A and B inhibitory (tribulin) activity during drug withdrawal anxiety

Morphine (10 mg/kg), ethanol (8% w/v, 2 ml/kg), nicotine (0.1 mg/kg), cannabis extract (200 mg/kg), lorazepam (10 mg/kg) and ondansetron (0.1 mg/kg) were each administered to rats twice daily i.p. for 14 days and the anxiogenic response following their withdrawal was monitored by the elevated plus-maze test 24 h later. Brains were removed and endogenous monoamine oxidase (MAO) A and B inhibitory activity (tribulin) levels measured on day 14 and 24 h after drug withdrawal in different groups of animals. Morphine, ethanol, lorazepam and nicotine withdrawal was associated with significant anxiety and corresponding increase in brain tribulin activity, particularly its MAO A inhibitory component. Cannabis and ondansetron withdrawal were neither associated with anxiety or change in tribulin levels. The investigation supports the postulated role of tribulin as an endogenous correlate of anxiety, its MAO A inhibitory component accounting for a major part of this effect.

Isatin is a potent endogenous antagonist of guanylate cyclase-coupled atrial natriuretic peptide receptors

Isatin (indole-2,3-dione) is an endogenous compound with anxiogenic properties. In the brain, highest levels (0.1 microgram/g) have been found in the rat hippocampus. In the present study, we show that isatin has little effect on a wide range of neurotransmitter and hormonal receptors but that it acts as an inhibitor of atrial natriuretic peptide (ANP) binding, with an IC50 of 4x 10(-7) M. It also inhibits ANP-activated particulate guanylate cyclase from rat kidney, heart and brain membranes in dose-dependent fashion, varying also with ANP concentration. These findings suggest that isatin is a new endogenous regulator of mammalian ANP activity, with potential implications for the control of both anxiety and natriuresis.

Migraine to the year 2000

Although migraine is inextricably bound up with 5-hydroxytryptamine and its many receptors, its precise mechanisms continue to elude us and there is still no clear evidence supporting either a vascular or neurogenic hypothesis unequivocally. What appears to distinguish migraine sufferers from normal subjects may be a greater gentic sensitivity to a wide variety of triggering agents--even including nitric oxide and the migraine aura, as well as those more usually recognized. Attention is drawn to a possible role for neurotrophins, such as the hyperalgesia-provoking nerve growth factor (NGF) in particular, as well as basic fibroblast growth factor (bFGF) and brain-derived neurotrophic factor (BDNF).

Monoamine oxidase A-inhibiting components of urinary tribulin: purification and identification

The endogenous monoamine oxidase (MAO) inhibitory activity, termed tribulin, contains several components. We have previously identified one of them, isatin, which is a selective inhibitor of MAO B. In the present study we have purified several further components of human urinary tribulin which act as selective inhibitors of MAO A. They have been identified by gas chromatography-mass spectrometry (GC-MS) as ethyl indole-3-acetate (and/or methyl indole-3-propionate), methyl indole-3-acetate and ethyl 4-hydroxyphenylacetate. IC50 values for MAO A were found to be 44 microM (105 microM for methyl indole-3-propionate), 88 microM and 120 microM, respectively, whilst those for MAO B were each greater than 1 mM. The artificial formation of these esters was excluded by carrying the parent acids, from which they are presumably synthesized, through the purification procedure. As tribulin output is increased during stress or anxiety, these results point to a possible role for tryptamine and tyramine pathways in such disorders.

Prevalence of antibodies against hepatitis A virus among new immigrants in Israel

Israel, located in a region endemic for hepatitis A virus (HAV), recently absorbed a large population of immigrants who came from the former USSR. To assess the risk of high morbidity in this population a serosurvey of HAV antibodies was undertaken. Serum samples were collected from 965 new immigrants, of whom 664 came from the European, non-endemic region, and 301 from the Asian and Caucasian endemic regions of the former Soviet Union. They were compared to 240 Israelis. Each population was divided into six age groups: 1-9, 10-19, 20-29, 30-39, 40-49, and 50 years of age and older. The Asian/Caucasian immigrants and the Israeli population were found to share similar characteristics. In both groups, antibodies to HAV (anti-HAV) were present in the 1-9-year-old age group and reached maximum prevalence (90% and 86.7%, respectively) in the 20-29-year-old age group. In contrast, among the European immigrants anti-HAV was first found in the 10-19-year-olds and peaked (93%) in the age group of 50 years and older. It is concluded that immigrants originating from the European part of the former USSR may require vaccination against hepatitis A.

Dietary migraine: recent progress in the red (and white) wine story

The concept of dietary migraine as a clinical entity remains controversial. We review here such objective evidence that has been put forward for its existence. Red wine, in particular, is commonly alleged to initiate attacks in susceptible individuals. We discuss how some of its recently described pharmacological properties might trigger off the sequence of events leading to migrainous headache.

5-Hydroxytryptamine release from platelets by different red wines: implications for migraine

We have confirmed our earlier finding that most red wines are able to bring about 5-hydroxytryptamine (5-HT, serotonin) release from platelets in vitro. Platelets from individual subjects manifested varying degrees of releasing ability but responded to different wines with a similar rank ordering. There was a high correlation (r = 0.87) between the effect of red wine and that of reserpine in different individuals. Some types of red wine caused a consistently higher release of 5-HT than others in all subjects; one red wine in particular resulted in negligible release. When several brands of this 'low-releasing' red wine were further examined, they all showed a lower activity than all the brands of a 'high-releasing' red wine type. This variation in releasing power was not related to intensity of red colour. Partial purification of red wine was achieved by column chromatography and showed releasing activity to be associated with a low molecular weight orange fraction. Preliminary studies, using solid phase extraction methods, showed that the active components lie mainly in a subgroup of the flavonoid fraction. If any of the adverse effects of red wine, such as headache induction, derive from this 5-HT releasing ability, then it may be possible to prepare red wines free from the chemical substances responsible.

Detoxified alcoholics, major depressives and tyramine sulphate excretion

The excretion of tyramine sulphate after challenge with an oral load of tyramine was assessed in recently detoxified, clinically depressed alcoholics and a matched group of major depressives. Tyramine excretion in the alcohol group (mean 5.95 ± 3.28 mg/3 h SD) was in the range previously observed in controls and was significantly higher than in the matched depressives (mean 3.43 ± 2.37 mg/3 h SD). Tyramine sulphate excretion has been suggested as a genetic vulnerability marker for major depression. This study suggests that depression associated with alcohol withdrawal is not characterised by decreased tyramine sulphate excretion after oral tyramine challenge, such decreased conjugation only being present, perhaps, in those patients with pre- existing endogenous depressive vulnerability. Although a genetic link between alcoholism and depression exists, these results support the absence of such a link to major depression.

Gut flora and the origin of some urinary aromatic phenolic compounds

The concentration of several phenolic acids and alcohols was measured in urine from germ-free and specific pathogen-free (SPF) rats before and after inoculation with faecal microorganisms, and from conventional rats before and after gut sterilization. The rate of excretion of benzoic acid, phenylacetic acid, and m- and p-hydroxyphenylpropionic acid in the germ-free animals was markedly increased after inoculation. Some acids showed no increase, including the endogenously generated homovanillic, vanilmandelic and p-hydroxyphenyllactic acids. Most others sought showed a small but significant increase. Some of the compounds excreted by the germ-free animals may have been in the food pellets, either as such or as precursors. The pattern was somewhat different in the SPF rats. The excretion of p-hydroxyphenylpropionic, p-hydroxyphenylacetic and m-hydroxyphenylacetic acids was initially much higher than in the germ-free animals and their excretion decreased after inoculation, presumably because of an altered pattern of gut flora. This work quantifies the effect of gut flora in the formation of some of the more important phenolic acids found in rat urine.

Mild hypomania (the highs) can be a feature of the first postpartum week. Association with later depression

About 10% of women show elation and associated features of hypomania in the first 5 days following childbirth. These symptoms can be detected using a self-rating scale (the 'Highs') based on SADS-L criteria. This phenomenon has been confirmed using the observer-rated Comprehensive Psychopathological Rating Scale, which also revealed a high degree of related irritability. Significantly more women scoring > or = 8 on the Highs scale at 3 days postpartum went on to manifest depression at 6 weeks than did subjects with no psychopathology in the early puerperium. It is suggested that the 'highs' followed by depression may be a mild and common form of bipolar disorder.

Metabolism of dopamine analogues in rat

1. The metabolism of dopamine analogues, differing in their ring substituents and length of side chain, has been examined in rat. 2. Both benzylamines and phenethylamines were converted to their analogous acids. Where sought, the corresponding alcohols were present only in minute traces, or were undetectable. 3. Benzylamines were largely excreted as such, possibly conjugated, and this output, together with acid metabolites, accounts for most of the dose. In contrast, only a minor part of the phenethylamine dose was excreted unchanged, and much of what was given remains unaccounted for. 4. With increasing chain length the proportion of the dose found as urinary metabolites decreases markedly; long-chain (hydrophobic) amines may be sequestered in fat depots rendering them largely unavailable for metabolism. 5. beta-Oxidation of long-chain aromatic acids is observed. 6. Catechols showed evidence of O-methylation, and some O-methyl compounds were demethylated. N-methylation and N-demethylation were, at best, very minor pathways. 7. No overall pattern emerged between the position of substituents and the extent of oxidation by monoamine oxidase. No pattern at all was apparent with the benzylamines. Phenethylamines showed a trend towards a lower rate of metabolism for secondary and tertiary amines. Phenethylamines and propylamines with ortho substituents exhibited a lower rate of metabolite excretion than did their analogues.