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At least 1,423 records · Page 79Linked to original sources
PubMed1976

Metabolism of biogenic amines in neuroblastoma and glioma cells in culture.

The kinetic parameters of monoamine oxidase (MAO; E.C 1.4.3.4) and catechol-O-methyltransferase (COMT; EC 2.1.1.6) were evaluated in extracts of adrenergic and non-adrenergic mouse neuroblastoma cells and in rat glioma cells. Using the naturally-occurring substrates tyramine, tryptamine, serotonin and norepinephrine, the affinity of MAO for a given substrate was independent of the presence of the catecholaminergic pathway or cell type used, with apparent Km values ranging from 8-14 microM for tryptamine to 510-580 microM for norepinephrine. The MAO activity in glioma cells was substantially greater than in either neuroblastoma clone, but Vmax values varied little with substrate among cell lines. Both the neuronal and glial COMT had a similar Km for 1-norepinephrine (200 microM); the corresponding Vmax values were also similar among the different cell lines, but represented only 2-10% of the maximal MAO activity. Neuroblastoma and glioma cells, when grown from early logarithmic to stationary phase, showed no significant changes in specific activity of either MAO or COMT. Growth of cells for 3 days with 1 mM-N6,O2'-dibutyryl adenosine-3',5'-cyclic monophosphate resulted in no marked change in either MAO or COMT activity. These results suggest that in neurons neither MAO nor COMT plays a major role in the type of transmitter inactivation that is analogous to that of acetylcholinesterase in cholinergic synapses. The occurrence of considerable MAO and acetylcholinesterase activities in glioma cells may indicate a role for these cells in neurotransmitter inactivation.

Acetylcholinesterase↗
PubMed1983

Biogenic amine-stimulated cyclic adenosine-3',5'-monophosphate formation in the rat carotid body.

The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body.

Adenosine↗
PubMed1984

Changes of biogenic amines and their metabolites in postmortem brains from patients with Alzheimer-type dementia.

Noradrenaline (NA), 3,4-dihydroxyphenylethylamine (dopamine, DA), 5-hydroxytryptamine (serotonin, 5-HT), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were measured in 22 regions of postmortem brains from four histologically verified cases with Alzheimer-type dementia (ATD) and nine histologically normal controls. Compared with the controls, concentrations of 5-HT and 5-HIAA in the ATD brains were significantly reduced in nine regions (superior frontal gyrus, insula, cingulate gyrus, amygdala, putamen, medial and lateral segments of globus pallidus, substantia nigra, lateral nucleus of thalamus) and in eight regions (amygdala, substantia innominata, caudate, putamen, medial and lateral segments of globus pallidus, medial and lateral nuclei of thalamus), respectively. NA concentrations of the ATD brains were significantly reduced in six regions (cingulate gyrus, substantia innominata, putamen, hypothalamus, medial nucleus of thalamus, raphe area). In contrast, significant reductions of DA and HVA concentrations in the ATD brains were found only in putamen and amygdala, respectively. The 5-HIAA/5-HT ratio in the ATD brains decreased significantly in locus coeruleus, while the HVA/DA ratio increased significantly in putamen and medial segment of globus pallidus. These findings suggest that the serotonergic and noradrenergic systems are affected, while the dopaminergic system is relatively unaffected in ATD brains.

Alzheimer Disease↗
PubMed1985

Vasoactive intestinal polypeptide receptors linked to an adenylate cyclase, and their relationship with biogenic amine- and somatostatin-sensitive adenylate cyclases on central neuronal and glial cells in primary cultures.

The presence of vasoactive intestinal polypeptide (VIP) receptors coupled to an adenylate cyclase was demonstrated on membranes of neurons or glial cells grown in primary cultures originating from the cerebral cortex, striatum, and mesencephalon of mouse embryos. A biphasic pattern of activation was observed in all these cell types, involving distinct high- and low-apparent-affinity mechanisms. The absence of additive effects of VIP and 3,4-dihydroxyphenylethylamine (DA, dopamine), isoproterenol (ISO), and 5-hydroxytryptamine (5-HT, serotonin) suggests that the peptide receptors are colocated with each of the corresponding amine receptors on neuronal membranes of the three structures studied. The nonadditivity between the VIP- and ISO-induced responses on cortical and striatal glial membranes reveals as well a colocation of VIP and beta-adrenergic-sensitive adenylate cyclases on the same cells. A subpopulation of mesencephalic glia could possess only one of the two types of receptors, as a partial additivity of the VIP and ISO responses was seen. In addition, VIP modified the characteristics of the somatostatin inhibitory effect on adenylate cyclase activity of neuronal membranes from the cerebral cortex and striatum but not from those of the mesencephalon. On striatal and mesencephalic glial membranes the somatostatin inhibitory effect was observed only in the presence of VIP. However, as previously seen with ISO, the presence of VIP did not allow the appearance of a somatostatin inhibitory response on cortical glial membranes. This suggests that cortical glia are devoid of somatostatin receptors.

Adenylyl Cyclases↗
PubMed1992

Alterations in extracellular and tissue levels of biogenic amines in rat brain induced by the serotonin2 receptor antagonist, ritanserin.

Systemic administration of ritanserin elicited rapid changes in dopamine (DA) and serotonin (5-HT) levels in both dialysate and neuronal tissue extracts. These effects occurred in both a site-selective and a dose-related manner. Increases in extracellular levels of DA and 5-HT in the nucleus accumbens were maximal at 120-140 min after treatment. A dose of 0.63 mg/kg of ritanserin elicited larger and more prolonged increases in extracellular DA and 5-HT levels than did the 0.3 mg/kg dose. By contrast, 0.63 mg/kg of ritanserin elicited no changes in either DA or 5-HT levels with dialysate collected from the striatum. Ritanserin also induced dose-related decreases in tissue levels of DA and 5-HT from the nucleus accumbens. The site specificity of action was again noted in that there were no dose-dependent decreases in tissue levels of DA or 5-HT measured from the striatum. Ritanserin exerted little effect on metabolite levels from either dialysate or tissue extracts. Taken together, these findings show that selective 5-HT2 receptor antagonism modulates DA and 5-HT neurotransmission in a specific manner. These actions appear to involve increased release of DA and 5-HT rather than significant changes in metabolism. These findings add further weight to the importance of 5-HT2 receptor interactions as an important component of antipsychotic activity.

Animals↗
PubMed1971

Effect of p-nitromethylamphetamine on biogenic amines and their amino-acid precursors in rat brain.

1. Low doses of p-nitromethylamphetamine caused small increases in the concentrations of brain noradrenaline and dopamine in the rat; a dose of 60 mg/kg however, caused a decrease in the concentrations of both amines. p-Nitromethylamphetamine caused behavioural hyperexcitability only at doses which approximated to half the LD50 (68 mg/kg).2. p-Nitromethylamphetamine potentiated the action of 4,alpha-dimethyl-m-tyramine in depleting brain noradrenaline. This suggests that it may affect brain noradrenaline concentrations by utilizing a reserpine resistant uptake mechanism.3. p-Nitromethylamphetamine decreased the concentration of brain 5-hydroxytryptamine.4. Changes in the blood and brain concentrations of tyrosine and gamma-amino-n-butyric acid concentration in the brain could not be correlated with the changes in brain amines. However, a rise in the concentration of brain tryptophan appeared to be correlated with the fall in brain 5-hydroxytryptamine.

Amino Acids↗
PubMed1974

Biogenic amines and head twitches in mice during ethanol withdrawal.

After chronic administration of ethanol to mice by the intragastric route head twitches occur as part of the ethanol withdrawal syndrome. Treatments which reduce brain 5-hydroxytryptamine or increase brain noradrenaline inhibited ethanol withdrawal head twitches, whereas treatments which increase brain 5-hydroxytryptamine or reduce brain noradrenaline were capable of inducing head twitches in control animals.

5-Hydroxytryptophan↗
PubMed1976

Effects of mazindol, a non-phenylethylamine anorexigenic agent, on biogenic amine levels and turnover rate.

1 Mazindol is a new anorexigenic agent which possesses a different chemical structure from that of phenylethylamines, but shows a pharmacological profile similar to that of (+)-amphetamine. 2 Mazindol neither altered whole brain monoamine levels (noradrenaline (NA), dopamine, 5-hydroxytryptamine (5-HT)) nor changed NA levels in the hypothalamus or dopamine levels in the caudate nucleus. 3 Mazindol enhanced dopamine turnover rate in the caudate nucleus, as shown by the increased rate of dopamine decline after blockade of catecholamine synthesis by alpha-methyl-p-tyrosine and decreased the conversion index of (3H)-tyrosine into brain NA. 4 Mazindol administration did not modify pargyline-induced decline of 5-hydroxyindoleacetic acid suggesting that 5-HT turnover is not altered by this drug.

Animals↗
PubMed1977

The fate of biogenic monoamines in perfused rabbit lung.

1. Inactivation of beta-phenylethylamine and several of its derivatives was studied in a preparation of rabbit lung perfused with Krebs physiological medium at 37 degrees C. Inactivation or removal of these compounds was calculated as the difference between the concentration of each amine in the perfusion medium and the effluent, collected separately from each lung. The extent of amine metabolic degradation was also measured, by column chromatography, in lung effluent. 2. With this technique the magnitude of amine removal as a function of concentration was determined and an apparent Km and Vmax of removal were calculated for each amine. 3. Percentage removal was highest with phenylethylamine (95%), and decreased, apparently in relation to increasing phenyl- and side chain-hydroxylation (and therefore likely increased hydrophilicity), and 5-hydroxytryptamine (64%), tyramine (53%), octopamine (35%), dopamine (32%) and noradrenaline (23%). 4. Inactivation of each amine could be accounted for by metabolic degradation to deaminated products, which appeared in lung effluent within 90 s of beginning amine perfusion. 5. When intrapulmonary metabolism of phenylethylamine was inhibited by simultaneous perfusion with semicarbazide (10 mM) and pargyline (10 micronM), the removal rate was unaltered, establishing that uptake of the amine from the vascular space is not dependent on metabolism at least for 4 min infusions.

Animals↗