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Results for “Dopamine”

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At least 19 recordsLinked to original sources

PubMed1979

A method to determine dopamine levels and turnover rate in discrete dopamine nerve terminal systems by quantitative use of dopamine fluorescence obtained by Falck--Hillarp methodology.

In tissue sections of regions with evenly distributed dopamine (DA) nerve terminals such as the nucleus caudatus, it is possible to obtain absolute amounts (nmol/g) of DA by means of quantitative microfluorimetrical measurements of catecholamine (CA) fluorescence intensity in the tissue and in DA-containing albumin-agar standards. The values agree well with mass-fragmentographical determinations of DA. The steady-state DA levels of heterogenously innervated areas such as the tuberculum olfactorium determined by quantitative microfluorimetry can be made comparable to the steady-state levels of DA obtained by biochemistry in the entire tuberculum olfactorium by means of a conversion factor which considers the dilution of the DA-containing structures by non-DA-containing nerve cells in the biochemical analysis. This factor is obtained by making biochemical determinations in such regions of untreated animals (e.g. the tuberculum olfactorium). The results of this paper have demonstrated that the histochemical approach not only has a high power of resolution and makes it possible to perform studies on an intact morphological substrate but also allows the determination of DA steady-state (nmol/g) and DA turnover rate (nmol/g x min-1) in discrete DA nerve terminal systems of the brain in absolute amounts.

Analysis of Variance↗

PubMed1978

Urinary dopamine in man and rat: effects of inorganic salts on dopamine excretion.

1. Plasma and urine free dopamine (3,4-dihydroxyphenethylamine) were measured in six normal male volunteer subjects and the urinary clearance of dopamine was calculated for each subject. 2. The excretion rates for free dopamine in man were greater than could be explained by simple renal clearance. It was concluded that free dopamine must, therefore, be formed in the kidney. 3. Changes in urinary dopamine excretion were studied in four groups of rats initially maintained on low sodium diet and then given equimolar dietary supplements of NaCl, NaHCO3, KCl or NH4Cl, to study the specificity of the previously observed increase in dopamine excretion after increased dietary NaCl. 4. The mean dopamine excretion increased significantly in rats given NaCl, KCl and NH4Cl, whereas dopamine excretion decreased in those given NaHCO3. 5. The failure of dopamine excretion to rise in response to loading with NaHCO3 was unexpected, and argues against a simple effect of volume expansion by the sodium ion. The increase in dopamine excretion with KCl and NH4Cl showed that this response was not specific to the sodium ion.

Adult↗

PubMed1979

Subcellular localization of dopamine in the anterior pituitary gland of the rat: apparent association of dopamine with prolactin secretory granules.

The subcellular compartmentalization of endogenous dopamine in the anterior pituitary gland of the rat was investigated using continuous sucrose density gradient centrifugation. When anterior pituitary homogenates were layered on continuous sucrose density gradients (1.0--2.0 M) and centrifuged for 60 min at 40,000 X g, dopamine recovered from the gradients was associated with two sets of subcellular particles. The particles in one set were recovered near the top of the gradient, whereas those in the other set were recovered near the bottom of the gradient in the region where particles containing PRL were also found. In fact, these dense dopamine-containing particles could not be separated from those particles which contained PRL. These findings were suggestive that dopamine and PRL were present in the same particle, viz. the PRL secretory granule. This interpretation was further strengthened when it was established that the PRL-containing granules were separable on the gradient from granules which contained GH, LH, FSH, ACTH, and TSH. When [3H]dopamine was added to the solution in which the anterior lobes were homogenized, no radio-activity was found to be associated with the dense dopamine-containing particles. Also, the addition of a large excess of nonradiolabeled dopamine at the time of homogenization did not influence the amount of dopamine associated with the dense particles. Thus, the apparent association of dopamine with PRL secretory granules was not an artifact of the homogenization process per se. Therefore, it is concluded that an association exists between intracellular dopamine and the PRL secretory granule.

Adrenocorticotropic Hormone↗

PubMed1976

Dopamine synthesis in rat brain striatal synaptosomes. II. Dibutyryl cyclic adenosine 3':5'-monophosphoric acid and 6-methyltetrahydropterine-induced synthesis increases without an increase in endogenous dopamine release.

The effects of N6, O2'-dibutyryl cyclic adenosine 3':5'-monophosphoric acid (dibutyryl cyclic AMP), DL-6-methyl-5, 6, 7, 8-tetrahydropterine (6-MPH4) and tyramine on dopamine synthesis and endogenous dopamine release in rat brain striatal synaptosomes have been examined. Dibutyryl cyclic AMP (1 mM) produced a 100% increase in dopamine synthesis but had no effect on endogenous dopamine release. Veratridine (75 muM) did not further stimulate dibutyryl cyclic AMP-treated tissue. 6-MPH4 (0.1 mM) also stimulated synthesis without stimulating dopamine release. The stimulation produced by 6-MPH4 was additive to the stimulations produced by either dibutyryl cyclic AMP or veratridine. Tyramine (10(-4) M) inhibited synthesis, while increasing dopamine release. These data suggest that 1) dopamine-releasing agents may have differential effects upon dopamine synthesis, depending on their mechanism of release, 2) dopamine synthesis can be stimulated independently of endogenous dopamine release and 3) the pteridine cofactor necessary for tyrosine hydroxylation is not normally present at saturating levels.

Animals↗

PubMed1978

Conformation of dopamine at the dopamine receptor.

Tritiated dopamine was used to label the dopamine receptor in membranes isolated from the rat corpus striatum. Scatchard analysis of displacement of [3H]dopamine by nonradioactive dopamine indicated the presence of two binding sites. The similarities in affinity, capacity, and drug specificity of the high-affinity site in the striatal membranes from rat and the binding site in the membranes from the calf caudate nucleus suggest that [3H]dopamine labels the same site in both species. In order to determine what conformation of dopamine is preferred at the dopamine receptor site, conformationally restricted analogs of dopamine--namely, the cis and trans 2-amino-1(3,4-dihydroxyphenyl)cyclobutane hydrochlorides--were tested for their affinity to the receptor. Compared to the cis conformation, the trans-restricted analogs had more affinity for the receptor site, indicating that dopamine probably interacts with the receptor in the trans conformation.

Animals↗

PubMed1979

Effects of intranigral administration of dopamine agonists and antagonists and baclofen on concentrations of dopac and dopamine in the striatum and substantia nigra of the rat.

Systemic administration of haloperidol to rats failed to alter the concentration of dopamine but increased the concentration of 3,4-dihydroxy-phenylacetic acid (DOPAC), the major metabolite of dopamine, in both the striatum and substantia nigra. These haloperidol-induced changes in DOPAC were prevented by an intranigral microinjection of baclofen, a drug which reduces nigrostriatal dopaminergic neuronal activity. It has been proposed that nigrostriatal neurons are regulated, in part, by the activation of autoreceptors in substantia nigra. However, intranigral microinjections of high concentrations of several dopaminergic antagonists failed to mimic the biochemical effects resulting from systemic administration of these drugs; instead, they slightly increased the concentrations of both dopamine and DOPAC in the striatum and decreased dopamine in substantia nigra. Intranigral microinjections of the dopamine agonist, apomorphine, failed to alter the concentration of DOPAC in the striatum, but reduced both dopamine and DOPAC in the nigra. If DOPAC concentrations reflect nigrostriatal dopaminergic neuronal activity, the present results suggest that dopaminergic agonists and antagonists acting in substantia nigra do not exert a major influence on the activity of these neurons.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1977

Dopamine uptake by platelets in hepatic encephalopathy; evidence for a possible depletion of brain dopamine.

A decrease in H3-dopamine uptake was demonstrated in the blood platelets of 22 hepatic encephalopathy (HE) patients when compared to that of patients with liver cirrhosis, but without HE, and controls. There was a direct correlation between the stage of HE and the decrease in H3-dopamine uptake. As blood platelets have characteristics similar to neurons which contain amines, they have been proposed as a model for the study of amine metabolism in neurological, as well as liver diseases. A defective dopamine uptake by the HE platelets suggests that a similar biochemical derangement is, also, present in the nerve cells of the dopaminergic system. This could account for the clinical evidence of extrapiramidal dysfunction and the arousal effect of levodopa in HE. Platelets from 10 cirrhosis, but HE-free, patients had a dopamine uptake which was intermediate between the HE patients and controls. When octopamine was added at the same concentrations as in serum of HE patients, the blood platelets from five controls showed a decrease in dopamine uptake proportional to the concentration of octopamine added. Octopamine may impair dopamine uptake by platelets from HE patients.

Adult↗

PubMed1979

Dopamine auto- and postsynaptic receptors: electrophysiological evidence for differential sensitivity to dopamine agonists.

The responses of dopamine cells in the substantia nigra to iontophoretically administered dopamine and intravenous apomorphine were compared to the responses of spontaneously active neurons in the caudate nucleus. Dopaminergic cells were six to ten times more sensitive to dopamine and intravenous apomorphine than 86 percent of the caudate cells tested. This differential sensitivity of dopamine auto- and postsynaptic receptors may explain the apparently paradoxical behavioral effects induced by small compared to large doses of some dopamine agonists and may provide a means of developing new types of drugs to antagonize dopaminergic influence in the central nervous system.

Action Potentials↗

PubMed1979

Haemodynamic effects of dopamine and dopamine combined with nitroglycerin in patients subjected to coronary bypass surgery.

The haemodynamic effects of dopamine and dopamine with nitroglycerin were evaluated in eight patients with coronary heart disease who underwent aortocoronary bypass surgery. The study was performed under anaesthesia and before surgery. Dopamine 8 micrograms kg-1 min-1 alone produced a marked increase of the cardiac index from 2.47 to 3.47 litre min-1 m-2 but only small changes in heart rate (from 65 to 68 beat min-1). This improvement in cardiac performance was accompanied by an increase of the mean pulmonary artery pressure from 10.9 to 21.3 mm Hg and in the left ventricular filling pressure from 6.1 to 13.8 mm Hg with unchanged systemic and pulmonary vascular resistance. Mean arterial pressure increased from 72 to 103 mm Hg. Simultaneous infusion of dopamine (8 micrograms kg-1 min-1) and nitroglycerin (mean dose 0.5 microgram 21.3 to 14.4 mm Hg) and of left ventricular filling pressure (from 13.8 to 7.9 mm Hg). Cardiac index (from 3.47 to 3.34 litre min-1 m-2) and mean arterial pressure (from 103 to 95 mm Hg) were not reduced to the same extent by the addition of nitroglycerin. The combined treatment of dopamine with nitroglycerine seems to be of value in patients with pre-existing high left ventricular filling pressure or with pulmonary hypertension.

Adult↗

PubMed1979

Enhancement of dopamine-induced stimulation of pancreatic secretion by 5-dimethyldithiocarbamylpicolinic acid (YP-279), a dopamine beta-hydroxylase inhibitor.

Effect of 5-dimethyldithiocarbamylpicolinic acid (YP-279), a dopamine beta-hydroxylase inhibitor, on the secretion of pancreatic juice induced by dopamine was investigated in preparations of the isolated blood-perfused canine pancreas. Either a single injection (300 micrograms) or an infusion (100 micrograms/min) of YP-279 intra-arterially (i.a.) caused no change in the outflow of the pancreatic juice, but the secretagogue effect of dopamine (1-10 micrograms, i.a.) was enhanced by the infusion of YP-279 (100 micrograms/min, i.a.) for 60 min. The previous conclusion obtained with fusaric acid was confirmed as follows; the dopamine beta-hydroxylase activity controls the dopaminergic mechanism of the pancreatic secretion.

Animals↗

PubMed1979

The cardiovascular pharmacology of 7-propyl-theo-phylline-dopamine (D4975); comparison with dopamine and dobutamine.

1 The effects of a newly developed dopamine-xanthine derivative, 7-propyl-theophylline-dopamine (D4975), have been examined in cats anaesthetized with sodium pentobarbitone. When administered intravenously (in doses as low as 0.5 to 1.0 micrograms/kg) it increased systemic arterial pressure, left ventricular (LV) dP/dtmax, dP/dt at fixed ventricular isovolumic pressures and cardiac output. Heart rate effects were minimal. 2 D4975 was about 5 times more active than dopamine or dobutamine in elevating LV dP/dtmax or dP/dt at common peak isovolumic pressures (CPIP) and about 10 times more active than dopamine at increasing systemic arterial blood pressure. The effects of D4975 were also more prolonged than those of the other two agents. 3 The effects of D4975 on LV dP/dtmax were greatly reduced by the prior administration of propranolol. D4975 has no effect on peripheral beta 2-adrenoceptors. 4 It is suggested that the effects of D4975 on the myocardium involve both beta 1-adrenoceptor stimulation and inhibition of phosphodiesterase and that the marked and prolonged pressor response is due to resistance to enzymatic breakdown by monoamine oxidase. 5 The results suggest that D4975 might prove valuable in the treatment of the hypotension and reduced myocardial contractility of shock, especially as it is possible to select a dose that increases LV dP/dtmax without increasing either heart rate of systemic arterial pressure.

Animals↗

PubMed1977

Dopamine receptors in rat striatum and nucleus accumbens; conformational studies using rigid analogues of dopamine.

A study was made of the actions of dopamine and of some 2-amino-1,2,3,4-tetrahydronaphthalenes on dopamine-sensitive adenylate cyclase in homogenates of rat striatum and nucleus accumbens. The compounds were also tested for their ability to stimulate motor activity following bilateral injection into the nucleus accumbens of conscious rats. The most active compounds on adenylate cyclase from both striatum and nucleus accumbens were dopamine and 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene(6,7-diOHATN). The 5,6-dihydroxy analogue (5,6-diOHATN) was 50 times less active than 6,7-diOHATN in striatal homogenates and 350 times less active in homogenates of nucleus accumbens. All dihydroxy compounds tested were active in causing stimulation of motor activity, the most active compounds being 6,7-and5,6diOHATN. Both dimethoxy derivatives tested were inactive on the adenylate cyclase and as locomotor stimulants.

Adenylyl Cyclases↗

PubMed1977

Correlation between serum dopamine-beta-hydroxylase activity and dopamine-beta-hydroxylase and tyrosine hydroxylase activities in central and peripheral adrenergic neurons and adrenal glands.

Serum dopamine-beta-hydroxylase activity in spontaneously hypertensive rats and Wistar-Kyoto rats had a positive correlation with dopamine-beta-hydroxylase and tyrosine hydroxylase activities in mesenteric vessels, vas deferens, and adrenal glands at 14-16 weeks of age, a negative correlation with dopamine-beta-hydroxylase activity in locus coeruleus at 3 weeks and 14-16 weeks of age, and a positive correlation with tyrosine hydroxylase activity only at 3 weeks of age, but not at 14-16 weeks of age.

Adrenal Glands↗

PubMed1979

Protein phosphorylation in rat caudate homogenate: stimulatory effects of dopamine and enhancement of dopamine response following 6-hydroxydopamine treatment.

Dopamine (3-hydroxytyramine) stimulates the incorporation of 32P into proteins endogenous to a homogenate of rat caudate nucleus when 10 microM [gamma-32P]-ATP is used as a substrate following preincubation with 400 microM ATP. The increase in 32P incorporation has pharmacological characteristics similar to caudate tissue. Chronic depletion of striatal dopamine in vivo by stereotaxic injection of 6-hydroxydopamine in the nigrostriatal pathway results in a significant enhancement of the dopamine stimulation of 32 p incorporation in vitro. Cyclic AMP-stimulated phosphorylation of caudate proteins remains unchanged following 6-hydroxydopamine treatment.

Adenosine Triphosphate↗

PubMed1979

Dopamine-beta-hydroxylase, adrenaline, noradrenaline and dopamine in the venous blood of adrenal gland of man: a comparison with levels in the periphery of the circulation.

In 10 human subjects plasma dopamine-beta-hydroxylase activity was found in the adrenal vein blood to be as high as in the periphery of the circulation. Adrenaline concentration in the adrenal vein blood was in the mean 170 times, noradrenaline concentration 11 times and dopamine concentration little higher than levels in the periphery.

Adrenal Glands↗

PubMedDate not supplied

The effect of alpha, alpha1-dipyridyl on noradrenaline, dopamine and 5-hydroxytryptamine levels and on dopamine-beta-hydroxylase activity in brain.

The effects of alpha, alpha1-dipyridyl (DP) on noradrenaline (NA), dopamine (DA) and 5-hydroxytryptamine (5-HT) levels in rat and mouse brain and on dopamine-beta-hydroxylase (DbetaH) activity in rat brain have been studied, DP decreases NA level and inhibits DbetaH activity in a dose dependent manner, without affecting DA or 5-HT levels.

2,2'-Dipyridyl↗

PubMed1975

Ultrastructure of the terminals of an identified dopamine-containing neurone markedby intracellular injection of radioactive dopamine.

The terminal processes of an identified dopamine-containing neurone in the central nervous system of the water snail were located for study with the electron microscope. This was achieved by intracellular injection of 3-H-dopamine followed by light and electron microscope autoradiography. The neurone showed extensive branching in ganglia whereprevious electrophysiological work had shown the presence of postsynaptic neurones. The terminal processes in these ganglia contained dense-cored vesicles of 50-250 nm diametersimilar to those in the perikaryon. Vesicles were found in large numbers in certain lacalized regions which may be synaptic terminals. The vesicles, which appear to take updopamine, tended to be smaller in the presumed terminal regions than in the preterminals and the perikaryon. No membrane specializations associated with typical synapses were observed.

Animals↗

PubMed1976

[Interactions of dopamine receptor agonists and antagonists with regard to dopamine synthesis and metabolism].

Intraperitioneal injection of d-amphetamine sulfate, 0.3-3 mg/kg, led to a marked rise in dopa formation in the dopamine rich areas c. striatum and mesolibbic cortex of the rat brain inhibiton of the aromatic amino acid decarboxylase with 3-hydroxybenzylhydrazine HCL (NSD 1015). However, amphetamine given in a dose of 10 mg/kg decreased the tyrosine hydroxylation rate in the mesolimbic cortex as well as the norepinephrine containing neocortex. In combination with haloperidol the stimulating effect of the neuroleptic on dopa formation was markedly potentiated by amphetamine in rat forebrain. Also, amphetamine potentiated the haloperidol induced increase in dopamine release in vivo measured as 3-methoxytyramine formation. The functional antagonists haloperidol and d-amphetamine appear to have synergistic effects on dopaminergic neurons.

Animals↗