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PubMed1977

Effect of hypercapnia and hypocapnia on tryptophan and tyrosine hydroxylation in rat brain.

The effects of induced hypo- and hypercapnia upon the rate of hydroxylation of tryptophan and tyrosine in the rat brain were studied by measuring the accumulation of 5-HTP and DOPA following administration of the aromatic L-aminoacid decarboxylase inhibitor 3-hydroxybenzylhydrazine HCl (NSD 1015). The results suggest that the hydroxylation of tryptophan varies directly with the tissue Po2. On the other hand, the hydroxylation of tyrosine did not show a simple relationship to Po2 but appeared to be influenced by pH changes.

5-Hydroxytryptophan↗
PubMed1978

Tryptamine-induced drug effects insensitive to serotoninergic antagonists: evidence of specific tryptaminergic receptor stimulation?

The drug effects of tryptamine and 5-hydroxytryptopham (5-HTP) in the rabbit were compared following monoamine oxidase inhibition and various drug pretreatments. Both agents evoked hyperthermia and behavioural excitation; tryptamine but not 5-HTP also produced forepaw clonic activity. Serotoninergic receptor blockers abolished the effects of 5-HTP but only weakly influenced tryptamine responses. Both tryptamine and 5-HTP effects were potentiated by fluoxetine. Methergoline, a putative tryptaminergic receptor blocker, antagonized tryptamine-induced hyperthermia and forepaw clonus but did not influence 5-HTP responses. It is postulated that while 5-HTP produces its effects through a serotoninergic mechanism, some of the responses to tryptamine result from activation of a specific tryptamine-sensitive mechanism.

5-Hydroxytryptophan↗
PubMed1977

Biogenic amine synthesis defect in dihydropteridine reductase deficiency.

In the enzymatic hydroxylation of aromatic amino acids, tetrahydrobiopterin is the essential cofactor. Regeneration of tetrahydrobiopterin requires dihydropteridine reductase, without which there should be a deficiency of hydroxylated amino acids and their products, biogenic amines. Assay of biopsied brain cortex of a patient with a deficiency of dihydropteridine reductases showed low concentrations of serotonin and dopamine, and this was reflected in the concentrations of their major metabolites measured in cerebrospinal fluid from lumbar, ventricular, and subarachnoid spaces. The metabolite concentrations were restored to normal, or above normal, by treatment with specific amino acids which bypass the metabolic block at the hydroxylation step. It is postulated that the seizures and neurological deterioration of the patient were related to a deficiency in the synthesis of biogenic amine neurotransmitters.

5-Hydroxytryptophan↗
PubMed1976

Failure to monoaminergic and cholinergic receptor blockers to prevent prostaglandin E2-induced luteinizing hormone release.

Receptor blocking drugs were used to determine whether adrenergic, dopaminergic, serotoninergic, or cholinergic synapses are involved in mediating the LH release induced by intraventricularly injected PGE2. Prostaglandin E2 (5mug) was injected into the 3rd ventricle (3rd V) of ovariectomized rats, and plasma LH concentrations before and after treatment were determined by radioimmunoassay. Phentolamine, 20 or 30 mug, or pronethalol, 20 mug (alpha and beta adrenergic receptor blockers, respectively) injected into the 3rd V failed to alter the elevation of plasma LH evoked by PGE2 injected into the ventricle 10 min later. Likewise, LH release following PGE2 was not changed when a dopaminergic blocker, pimozide (0.63 mg/kg, SC), was injected 2 h prior to PGE2. Two antagonists of serotonin, methysergide maleate (3 mg/kg ip) or cinanserin HC1 (1 mg/kg iv) given 2 h or 45 min before PGE2, respectively, failed to alter the action of PGE2. Atropine (100 or 250 mug) injected into the 3rd V 10 min prior to PGE2 was also ineffective in blocking the increase in plasma LH following PGE2. The results of this study indicate that the effect of PGE2 on LH release is not mediated by adrenergic, dopaminergic, serotoninergic, or cholinergic receptors. They also suggest that PGE2 is not acting trans-synaptically but probably directly on the LHRH neuron to induce the discharge of LHRH into the hypophysial portal vessels which then evokes release of LH from the adenohypophysis.

5-Hydroxytryptophan↗
PubMed1976

Neurotransmitter regulation of growth hormone and ACTH in the rhesus monkey: effects of biogenic amines.

In an attempt to clarify the role of central neurotransmitters in GH and ACTH regulation, chair-adapted unanesthetized adult male rhesus monkeys and chronic indwelling intratrial cannulae were given 30 min infusions of various agonists known to affect central amines, and plasma samples were withdrawn for GH and cortisol determinations. Infusion of acid-saline vehicle alone had no significant effect on plasma GH or cortisol (P less than 0.05). L-Dihydroxyphenylalanine (L-Dopa) (4.5 and 45 mg/kg), but not apomorphine (7 mug/kg), a specific dopaminergic agonist, produced significant elevations of GH. Both noradrenergic (clonidine HCl, 1.5, 15, and 150 mug/kg, and D,L-threodihydroxyphenylserine (D,L-threodops) 90 mg/kg) and serotoninergic (5-hydroxy-L-tryptophan (5-HTP), 45 mg/kg) agonists induced significant GH responses. These findings suggest that GH is regulated in the rhesus monkey by noradrenergic and serotoninergic neurons, whereas participation of dopaminergic neurons has not been established. Significant cortisol responses were only observed following infusion of 5HTP (45 mg/kg). Dopaminergic and noradrenergic agonists not only failed to alter resting cortisol levels but also did not affect the cortisol response to 5-HTP. In the rhesus monkey serotoninergic mechanisms appear to be responsible for the regulation of resting cortisol levels. A catecholamine inhibitory mechanism was not demonstrated in this species.

5-Hydroxytryptophan↗
PubMed1976

Glucocorticoid regulation of the serotonergic system of the brain.

Glucorticoids at concentrations above 10(-7) M stimulate the uptake of tryptophan by brain synaptosomes. Furthermore, in both developmental and drug-induced (reserpine and ethanol) increases of brain tryptophan hydroxylase activity, glucocorticoids are required in order for the increases to occur. If de novo enzyme synthesis is assumed to take place in such increases, we could adopt the working hypothesis that two loci of glucocorticoid action may exist in serotonergic neurons with respect to their specific function: one in the cell body presumably in a sequence of macromolecular events, and the other directly on nerve terminals. Thus, in its immediate action, the hormone may rapidly regulate 5-HT synthesis through an increased uptake of tryptophan by nerve terminals. In the slow action, the hormone may mainly play a permissive role in the induction of tryptophan hydroxylase by factors yet to be identified.

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PubMed1976

Review of drug treatment for Down's syndrome persons.

A review of drug treatment for Down's syndrome individuals was presented. Drugs used to modify behavior, as well as drugs used with the goal of affecting cognitive processes, were discussed. Some observations were offered as to the effectiveness of past and current drugs on Down's syndrome and some methodological problems relating to drug studies presented. There have not been any drugs that have demonstrated remarkable improvement in the status of Down's syndrome individuals that have been widely accepted as effective.

5-Hydroxytryptophan↗
PubMed1977

Synthetic melanocyte stimulating hormone release-inhibiting factor (MIF). Part III: effect of L-prolyl-N-methyl-D-leucyl-glycinamide and MIF on biogenic amine turnover.

The effect of the factor that inhibits the release of melanocyte stimulating hormone (MSH), i.e., L-prolyl-L-leucyl-glycinamide (MIF), and L-prolyl-N-methyl-D-leucyl-glycinamide, an analog, on brain norepinephrine (NE), dopamine (DA) and serotonin (5-HT) turnover was examined in rats. The analog (40 mg/kg i.p.), in a fashion similar to MIF (40 and 5 mg/kg i.p.), increased brain DA turnover; only MIF (40 mg/kg i.p.) increased endogenous DA levels. The analog (40 and 5 mg/kg i.p.) decreased brain NE turnover; MIF at the same doses was ineffective. Neither MIF nor the analog affected rat brain 5-HT turnover or the 5-HTP-induced behavioural syndrome in the mouse. These results indicate that the analog, like MIF, exerts effects on central catecholamine turnover. The different biochemical profile of the analog compared to MIF may be importance with regard to potential clinical use in the treatment of Parkinson's disease and depression.

5-Hydroxytryptophan↗
PubMed1976

Analysis for indole compounds in urine by high-performance liquid chromatography with fluorometric detection.

We describe a chromatographic system involving a high-performance chemically-bonded reverse-phase column and fluorescence detection for measurement of indoles in urine. We controlled retention and selectivity by optimizing the methanol content and pH of the mobile phase. Six reference indoles were separated in less than 20 min; three 5-hydroxyindoles were eluted in less than 7 min. About 5-15 ng of aqueous solutions of these compounds can be detected. The combination of selectivity (from use of the chromatographic column) and fluorescence detection permitted analysis for five of the six indoles after a single urine-deproteinization step.

5-Hydroxytryptophan↗
PubMed1977

[Metabolic disorders in experimental hepatic insufficiency and parenteral feeding].

Anhepatia is a complete experimental model for the study of metabolic disturbances associated with hepatic insufficiency. The authors report their experience based upon 16 cases of total hepatectomy in the dog. The animals received different types of hepatic assistance : group 1 (2 dogs), carbohydrate assistance (glucose 7 g/kg/24 h) ; group II (2 dogs), carbohydrate and haemostatic assistance : homologous plasma 50 ml/kg body weight per 24 hours previously stored at - 80 degrees C ; group III (2 dogs) same nutrition as in group II, combined with amino acids : leucine 53, 3 mg, isoleucine 46, 6 mg ; valine 53,3 mg alpha-ketonic acid (lg/kg/24 h) ; group IV (10 dogs, same nutrition as in group III, combined with supplements in neuro transmitter precursors : 6 dopa 1,66 mg, 5 hydroxy-tryptophane 2 mg and choline 16, 66 mg/kg/24h. Metabolic disturbances and their course were analysed in detail. Results : (mean survival) - group I : 24 +/- 4 hours; group II : 36 +/- 9 hours; group III : 42 +/- 4 hours; group IV : 90 +/- 9 hours. The average survival differed significantly for groups III and IV (p less than 0,01) in comparison with control groups I and II. The replacement of essential hepatic functions such as blood glucose regulation, coagulation, detoxication and the provision of neurotransmitter precursors made possible 4 days survival after total hepatectomy.

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