Amount Of Serotonin Research Articles

Modulation of affinity of postsynaptic serotonin receptors by antidepressant drugs.

Antidepressant drugs are generally thought to act by changing aminergic neurotransmission. Thus, according to the indoleamine hypothesis1, antidepressant drugs increase the amount of serotonin (5-HT) available at the receptor level by inhibition either of 5-HT uptake or of its degradative enzyme (monoamine oxidase)2. Various experimental observations have, however, suggested that the effects of antidepressant drugs may be located at the postsynaptic receptor level3–7. We report here that antidepressant drugs alter the structural conformation of the postsynaptic serotoninergic receptor in synaptosomal membranes isolated from rat and horse brains in such a way as to inactivate them.

A rapid non-destructive fluorometric assay for gangliosides

An assay for gangliosides has been developed which is both rapid and non-destructive. The procedure is based on specific ganglioside serotonin binding and utilizes the inverse relationship between serotonin dialysis rates and ganglioside concentrations. The amount of serotonin in the diffusate after 30 minutes of dialysis is measured fluorometrically and converted, via a standard curve, to ganglioside content. Samples containing as little as 10 nanomoles of ganglioside have been assayed. A single assay is complete in 30 minutes and triplicate assays require less than an hour. Since no hydrolysis or other chemical reaction is involved, samples can be recovered intact by further dialysis and lyophilization.

Cardioactive substances in blood: The actions of serotonin on isolated guinea-pig atria

1. 1. Serotonin has cardioactive effects on several isolated heart muscle preparations. 2. 2. Serotonin derives from platelets and the handling of blood samples affects the amount released into serum or plasma. 3. 3. The inotropic effect of serum or plasma on guinea-pig atria may be accounted for by the amount of serotonin in the sample, as determined chemically. 4. 4. Serotonin may obscure effects due to substances with lower activity. 5. 5. Qualitative aspects of the response to substances in blood help to identify them; these include time course of the response, slope of the dose response curve, and concordance, or not, of inotropic and chronotropic responses.

Reversal by arginine-vasotocin of the effects of pinealectomy on the amount of 5-hydroxytryptamine in the hypothalamus and the concentrations of luteinizing hormone and follicle-stimulating hormone in the plasma of immature male rats.

Pinealectomy in immature (25-day-old) male Wistar rats significantly decreased the content of 5-hydroxytryptamine (5-HT) in the hypothalamus and increased concentrations of plasma LH and FSH 3 days after surgery. Extremely small amounts (10(-4) pg) of arginine-vasotocin (AVT) injected into the third ventricle (pineal recess) 5 min after pinealectomy completely prevented the decrease in the hypothalamic content of 5-HT and the increase in the concentration of LH and FSH in the plasma. It is suggested that AVT prevented the increase of plasma levels of LH and FSH after pinealectomy by increasing levels of 5-HT at postsynaptic receptor sites.

Cerebral arterial spasm. 3. In vivo intracisternal production of spasm by serotonin and blood and its reversal by phenoxybenzamine.

✓ In vivo experiments in dogs demonstrated that physiological concentrations of serotonin, when injected intracisternally, caused cerebral arterial spasm that lasted for at least 3 hours. Comparable spasm was produced by the injection of blood containing approximately the same amount of serotonin. Phenoxybenzamine reversed both the spasm produced by pure serotonin and that produced by blood. A hypothesis of the etiology of cerebral arterial spasm is proposed based on the experimental results of the entire study.

Postsynaptic adrenergic-cyclic AMP control of the serotonin content of cultured rat pineal glands.

Abstract— This investigation was designed to determine whether the amount of serotonin (5‐HT) in cultured pineal glands can be altered by norepinephrine (NE). Treatment with l‐NE (10−5‐10−7m) for 4‐6 h caused a gradual decrease in the concentration of 5‐HT to a value that was less than 30% of that in the untreated control gland. This effect was observed using chronically denervated pineal glands. d‐Norepinephrine (10−6‐10−7m) and dopamine (10−4m) were ineffective in lowering 5‐HT. The effect of l‐NE was completely blocked by a β‐adrenergic receptor blocker, propranolol and was only slightly decreased by α‐adrenergic receptor blockers. These observations indicate that l‐NE acts post‐synaptically via a highly specific β‐adrenergic mechanism. The effect of l‐norepinephrine was mimicked by theophylline and N6, 2′0‐dibutyryl adenosine 3′,5′‐monophosphate, an indication that adenosine 3′,5′‐monophosphate is involved in the effect of l‐NE on 5‐HT. Treatment with cycloheximide, which by itself caused a decrease in pineal 5‐HT, also blocked any further decrease caused by treatment with l‐NE, an indication that protein synthesis is necessary for maintenance of baseline levels of serotonin and for the effect of l‐NE to be observed. The total amount of l‐[3H]NE and degradation products of L‐[3H]NE in the gland after 6 h of treatment with l‐[3H]NE was less than 3 pmol. This amount of l‐NE and degradation products of l‐NE could not account for the decrease of 100‐200 pmol of 5‐HT on the basis of a mole for mole replacement of 5‐HT by l‐NE. These findings are consistent with the hypothesis that non‐neuronal pineal 5‐HT is physiologically regulated by the release of l‐NE from the sympathetic nerve network.

Biochemical research in two cases of endogenous pellagra.

Our studies were carried out on two patients with clinical symptoms of pellagra. The biochemical results indicated hypoaminoaciduria with markedly increased urinary excretion of indican and a normal blood serotonin. The tryptophan load test was followed by an increased urinary excretion of indican and by a decreased approximately (40–50%) amount of serotonin in the blood. Since our patients had normal dietary foods, the clinical signs could not be of classical pellagra. On the other hand, the absence of hyperaminoaciduria makes diagnosis of Hartnup disease impossible. Therefore, the most probable form seems to be endogenous pellagra.

Influence of monoamine oxidase inhibitors on 5-hydroxytryptamine synthesis in the brain.

SummaryTwo hydrazine (βenylisopro-pylhydrazine and iproniazid) and 2 non-hydrazine (trans-2 phenyclyclolamine and pargyline) monoamine oxidase inhibitors were tested for their influence on the conversion of tryptophan and 5-hydroxytrypto-phan to 5-hydroxytryptamine. It was found that the conversion of 5-hydroxytryptophan was influenced by both types of monoamine oxidase inhibitors but the non-hydrazine inhibitors were most effective. There was an increase in the amount of 5-hydroxytryptamine formed, especially during the first few hours after the inhibitors were administered. Tryptophan conversion to 5-hydroxytryptamine was not significantly influenced by the monoamine oxidase inhibitors. Excitatory responses seen with monoamine oxidase inhibitors and 5-hydroxytryptamine precursors were also observed and appeared to be related to the degree of enzyme inhibition more than to the amount of 5-hydroxytryptamine.

Circadian Rhythm in Pineal Serotonin: Effect of Monoamine Oxidase Inhibition and Reserpine

The pineal gland of the rat shows a circadian rhythm in its serotonin content, the amount of serotonin decreasing at night. This decrease can be prevented by inhibiting the action of monoamine oxidase. Reserpine abolishes the circadian rhythm in pineal serotonin in the same manner as does interruption of the sympathetic nervous connections of the central nervous system and the pineal gland. These observations suggest that circadian changes in release and binding of serotonin may occur in the pineal gland, and that a central mechanism in which monoamines participate may control the circadian pineal-serotonin rhythm.

THE EFFECT OF GAMMA-IRRADIATION ON THE AMOUNT OF 5-HYDROXYTRYPTAMINE IN THE GUT AND SPLEEN IN THE EARLY PHASE AFTER IRRADIATION.

24 et 48 h apres irradiation-γ (900 r) la quantite de 5-hydroxytryptamine dans l'intestin du rat n'a pas change de maniere significative. La quantite de 5-hydroxytryptamine dans la rate du rat, exprimee par g de tissu frais a augmente. Le pretraitement avec de la cysteamine abaisse nettement la quantite de 5-hydroxytryptamine dans la rate, apres l'irradiation.

Change in the serotonin content of the blood of rabbits following typhoid intoxication

The content of serotonin in the blood, brain, small intestine, lungs and skin undergoes phasic changes during the process of typhoid intoxication in rabbits. The amount of serotonin in the blood and organs drops markedly 15 min after intravenous injection of typhoid vaccine and remains below the initial level for a long period of time. The rise of serotonin level in the organs begins earlier than in the blood. In 12 hours after the administration of the vaccine, serotonin concentration considerably exceeds its initial level in the blood and organs. Repeated reduction of serotonin content is seen in 24 hr.

THE EFFECT OF DIET ON THE 5‐HYDROXYTRYPTAMINE CONTENT OF THE SMALL INTESTINE AND OTHER ORGANS IN RATS AND MICE

In rats, a diet of meat or liver caused a rise in the amount of 5-hydroxytryptamine in the small intestine, an increase in the weight of the intestine and a 10-fold increase in anaerobic bacteria in the rectum. A diet containing added tryptophan did not affect tissue levels of 5-hydroxytryptamine in rats, but in mice there was a rise of 5-hydroxytryptamine in various tissues. The significance of these findings is discussed together with the possible role of intestinal bacteria in mediating the effects caused by a meat diet. No change was observed in the 5-hydroxytryptamine content of brain or in the distribution of argentaffin cells in the jejunum as a result of these diets.

Further Studies on the Biosynthesis of 5-Hydroxytryptamine

Abstract The factors affecting the 5-hydroxytryptophan decarboxylase activity of the brain of animals have been studied. By altering the conditions of incubation and the amounts of the constituents of the incubation mixture, the activity as determined by the amount of 5-hydroxytryptamine formed has been increased about 10-fold. Intramuscular injections of cortisone and prednisolone did not reduce the enzyme activity although such treatment lowers the 5-hydroxytryptamine content of several tissues.

The effect of substance P on the amount of 5-Hydroxytryptamine in the gut

L'injection intrapéritonéale de la substanceP (60 à 120 U/kg) chez le rat provoque une augmentation marquée de 5-HT dans la paroi de l'estomac et dans l'iléon. Dans la rate de cet animal, on n'y observe pas d'augmentation de 5-HT. L'administration intraluminale de la substanceP (60–80 U) dans l'iléon isolé du cobaye, augmente aussi sensiblement la quantité de 5-HT.

The relationship between 5-hydroxytryptamine and adenosine triphosphate in blood platelets.

In normal platelets a proportionality was found between the amount of adenosine triphosphate (ATP) and amount of 5-hydroxytryptamine (5-HT) in platelets both before and after incubating them in plasma to which 5-HT had been added. In patients receiving reserpine and in others with myeloid leukaemia, the amount of 5-HT in the platelets and the uptake of 5-HT by them were depressed, while the amount of ATP was normal. The possibility that ATP is involved in the accumulation of 5-HT by platelets is discussed.

Pharmacological and biochemical study of a carcinoid tumor.

SummaryThe pharmacological activity and fluorescence characteristics of extracts of an appendiceal carcinoid tumor could be accounted for entirely by its serotonin content. The amount of serotonin in the carcinoid tissue was about 1000 times that of normal tissue, and its enzymatic ability to form serotonin from 5-hydroxytryptophane was about 35 times that of normal human appendiceal tissue.