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  • 1
    Electronic Resource
    Electronic Resource
    α2-Adrenergic Receptors in Neuronal and Glial Cultures: Characterization and Comparison (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 53 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Membranes prepared from either neuronal or glial cultures contain α2-adrenergic receptors as determined by the characteristics of [3H]yohimbine ([3H]YOH) binding. The binding was rapid, reversible, saturable, dependent on the protein concentration used, and reached equilibrium by 5 min in membranes from both neuronal and glial cultures. Scatchard analyses of saturation isotherms revealed similar KD values of 13.7 ± 1.35 nM (n = 10) for neuronal cultures and 18.42 ± 2.34 nM (n = 10) for glial cultures. Glial cultures contained many more binding sites for [3H]YOH than neuronal cultures, having a 5max of 1.6 ± 0.33 pmol/mg protein (n = 10) compared with 0.143 ± 0.018 pmol/mg protein (n = 10) in neurons. Drugs selective for α2-adrenergic receptors were the most effective displacers of [3H]YOH binding in both neuronal and glial cultures, i.e., the α2-adrenergic antagonists rauwolscine and yohimbine were better displacers than the other catecholamine antagonists prazosin, corynan-thine, or propranolol. The agonists showed the same pattern with the α2-selective drugs clonidine and naphazoline being the most effective competitors for the [3H]YOH site. GTP and its nonhydrolyzable analog, 5′-guanylyl-imidodiphos-phate, were able to lower the affinity of the α2-receptors for agonists but not antagonists in membranes from both neuronal and glial cultures, suggesting that the receptors are linked to a G protein in both cell types. The presence of α2-adrenergic receptors in neuronal cultures was also substantiated by light microscopic autoradiography of [3H]YOH binding. In summary, we have demonstrated that both neuronal and glial cultures contain α-adrenoceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb07326.x
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  • 2
    Electronic Resource
    Electronic Resource
    Characteristics of the β-Adrenoreceptor from Neuronal and Glial Cells in Primary Cultures of Rat Brain (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The cellular characteristics of the β-adrenoreceptor in glial and neuronal cells from the newborn rat brain were determined by (−)-[125I]iodocyanopindolol binding. In membranes from both cell types, the binding was saturable and from competition assays the potency series of (−)-isoproterenol 〉 (−)-epinephrine = (−)-norepinephrine 〉 (+)-isoproterenol was observed. 5′-GuanylyI-imidodiphosphate reduced the affinity of (−)-isoproterenol for the β-adrenoreceptor from glial cells but had no effect on agonist affinity in neuronal cells. Chronic treatment of both cell types with (−)-isoproterenol reduced the receptor content and the capacity of the agonist to increase the cellular cyclic AMP content. However, the receptor recovery after chronic agonist treatment was faster in glial cells (72 h) than neuronal cells (120 h) and was blocked by cycloheximide. Treatment of both types with the irreversible β-blocker bromoacetylalprenololmentane (2 μM) reduced the receptor content by 78% but no receptor recovery was observed for 120 h after the initial receptor loss. The data indicated that the majority of β-adrenoreceptors in both cell types are the β−1 subtype, but show some differences in receptor-agonist interactions. Furthermore, these CNS cells may be useful models for regulatory studies on the β-adrenoreceptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00757.x
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  • 3
    Electronic Resource
    Electronic Resource
    α1-Adrenergic Receptor-Mediated Downregulation of Angiotensin II Receptors in Neuronal Cultures (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Previous evidence has suggested that brain catecholamine levels are important in the regulation of central angiotensin II receptors. In the present study, the effects of norepinephrine and 3,4-dihydroxyphenylethylamine (dopamine) on angiotensin II receptor regulation in neuronal cultures from rat hypothalamus and brainstem have been examined. Both catecholamines elicit significant decreases in [125I]angiotensin II-specific binding to neuronal cultures prepared from normotensive rats, effects that are dose dependent and that are maximal within 4–8 h of preincubation. Saturation and Scatchard analyses revealed that the norepinephrine-induced decrease in the binding is due to a decrease in the number of angiotensin II receptors in neuronal cultures, with little effect on the receptor affinity. Norepinephrine has no significant actions on [125I]angiotensin II binding in cultures prepared from spontaneously hyper tensive rats. The downregulation of angiotensin II receptors by norepinephrine or dopamine is blocked by α1-adrenergic and not by other adrenergic antagonists, a result suggesting that this effect is initiated at the cell surface involving α1-adrenergic receptors. This is further supported by our data indicating a parallel downregulation of specific α1-adrenergic receptors elicited by norepinephrine. In summary, these results show that norepinephrine and dopamine are able to alter the regulation of neuronal angiotensin II receptors by acting at α1-adrenergic receptors, which is a novel finding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00729.x
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  • 4
    Electronic Resource
    Electronic Resource
    α1-Adrenergic Receptors in Neuronal Cultures from Rat Brain: Increased Expression in the Spontaneously Hypertensive Rat (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Neuronal cells in primary culture from 1-day-old brains of normotensive, Wistar-Kyoto strain (WKY) and spontaneously hypertensive (SH) rats have been utilized to study the expression of α1-adrenergic receptors. Binding of a selective α1 antagonist, [125I]2-[β-(4-hydroxy-3-iodophenyl)-ethylaminomethyl]-tetralone ([125I]HEAT) to neuronal membranes prepared from primary brain cultures of WKY and SH rats was 75–80% specific, rapid, and time-dependent although the binding was 1.5–2 times higher in neuronal membranes from SH rat brain cultures. Kinetic analysis of the association and dissociation data demonstrated no significant differences between rat strains. Competition-inhibition experiments provided IC50 values for various antagonists and agonists in the following order: prazosin 〈 phentolamine 〈 yohimbine 〈 phenylephrine 〈 norepinephrine 〈 propranolol, suggesting that [125I]-HEAT bound selectively to α1-adrenergic receptors. Scatchard analysis of the binding data provided straight lines for both strains of rats, indicating the presence of a homogeneous population of binding sites. It also showed that the increase in the binding in neuronal cells from SH rat brains over those from normotensive WKY controls was a result of an increase in the number of α1-adrenergic receptors. Incubation of neuronal cultures from both strains of rats with phenylephrine, an α1-adrenergic agonist, caused a time- and dose-dependent decrease in the binding of [125I]HEAT. This decrease was due to a decrease in the number of α1-adrenergic receptors. In conclusion, we demonstrated that the expression of α1-adrenergic receptors in neuronal cultures of SH rat brain was increased compared with neuronal cultures from normotensive controls. We suggest that the elevated number of these receptors in neurons from the brains of SH rats is an intrinsic property of these cells and therefore provides an etiological basis for the predisposition of these animals to the hypertensive state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00739.x
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  • 5
    Electronic Resource
    Electronic Resource
    Phorbol Ester-Induced Upregulation of Angiotensin II Receptors in Neuronal Cultures Is Potentiated by a Calcium Ionophore (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous studies have suggested that protein ki-nase C is important in the regulation of angiotensin II receptors in neuronal cultures, because the C-kinase agonists, phorbol esters, are able to increase the number of these receptors. In the present study, we have further investigated the role of protein kinase C in angiotensin II receptor regulation. This enzyme is calcium dependent, and so we investigated the effects of A23187, a calcium ionophore, on phorbol ester-stimulated and basal angiotensin II receptor regulation. A23187, at concentrations that increased 45Ca2+ influx, caused a dose-dependent potentiation of phorbol-12-myristate-13-acetate (TPA)-stimulated upregulation of angiotensin II receptors. This potentiation by A23187 was a further increase in angiotensin II receptor number and was abolished in calcium-free medium. In the absence of TPA, A23187 caused a decrease in angiotensin II receptor number, an effect not observed in calcium-free medium. The results suggest at least two pathways for angiotensin II receptor regulation in neuronal cells: (a) by calcium-dependent protein kinase C and (b) via an influx of calcium into the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb04849.x
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  • 6
    Electronic Resource
    Electronic Resource
    Irreversible Binding and Recovery of the Norepinephrine Uptake System Using an Alkylating Derivative of Norepinephrine (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 50 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of bromoacetylaminomenthylnorepinephrine (BAAN) on the sodium-dependent, high-affinity norepinephrine (NE) uptake system in rat brain synaptosomes and CNS neuronal cultures were investigated. BAAN inhibited [3H]NE uptake into synaptosomes in a dose- and time-dependent manner (IC50. 6.5 μM). Pretreatment of cortical synaptosomes or neuronal cells with BAAN alone, followed by washing to remove free drug, reduced the Vmax but did not alter the Km value for [3H]NE uptake. The BAAN-induced reduction in Vmax was attenuated by concurrent pretreatment with desipramine and blocked by the reaction of BAAN with dithiothreitol or cysteine. In contrast, BAAN was 19-fold less potent at inhibiting [3H]dopamine uptake in striatal synaptosomes, and no change in the Vmas or Km value for [3H]dopamine uptake was observed after a pretreatment with BAAN followed by washing. Furthermore, the irreversible β-antagonist, bromoacetylalprenololmentane, was equipotent to BAAN for inhibiting [3H]NE uptake into cortical synapto somes, but did not alter the Vmax or Km for [3H]NE after pretreatment. In neuronal cultures, BAAN inhibited sodium-dependent uptake of [3H]NE (IC50, 5.6 μM) with no effect on sodium-independent uptake. After pretreatment of cultures with 30 μM BAAN followed by washing, there was a 74% decrease in the Vmax for [3H]NE uptake. Following a 24-h lag period, uptake recovered to the control level within 48 h; however, recovery was completely blocked by cycloheximide. The data indicate that BAAN irreversibly binds to the [3H]NE uptake system in both CNS synaptosomes and neuronal cultures and may be a useful probe for studying the turnover of the [3H]NE uptake system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb10571.x
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  • 7
    Electronic Resource
    Electronic Resource
    Protein Kinase C Agonists Increase the Expression of Angiotensin II Receptors in Neuronal Cultures (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Previous studies have shown that norepinephrine is important in the regulation of central angiotensin II receptors, an effect mediated by α1-adrenergic receptors. Because α1-adrenergic stimulation leads to inositol phospholipid hydrolysis and activation of protein kinase C, we have examined a possible role of this enzyme in the regulation of central angiotensin II (Ang II) receptors. In the present study, we have examined the effects of protein kinase C activators, phorbol esters, on the expression of Ang II receptors in neuronal cultures prepared from 1-day-old rat brains. The active phorbol ester phorbol- 12-myristate-13-acetate (TPA) caused time- and concentration-dependent increases in the specific binding of [125I]Ang II to its receptors in neuronal cultures of normotensive and spontaneously hypertensive rat brains. The stimulatory effect of TPA on Ang II receptors was apparent within 15 min and reached a maximum between 1 and 2 h. Ang II specific binding had returned to control levels by 24 h. Various phorbol esters increased [125I]Ang II binding in accordance with their order of potency in stimulating protein kinase C activity. Saturation and Scatchard analysis revealed that the phorbol ester-induced increase in [125I]Ang II binding was due to an increase in the number of Ang II receptors. These observations indicate that activation of protein kinase C results in an increased expression of Ang II receptors in neuronal cultures from both normotensive and spontaneously hypertensive rat brains. The results suggest a possible role of phosphorylation in Ang II receptor expression in neuronal cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb05760.x
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  • 8
    Electronic Resource
    Electronic Resource
    Lack of alpha-1-adrenergic receptor-mediated downregulation of angiotensin II receptors in neuronal cultures from spontaneously hypertensive rat brain (1989)
    Springer
    Molecular and cellular biochemistry 91 (1989), S. 111-115 
    Details
    ISSN: 1573-4919
    Keywords: angiotensin receptors ; norepinephrine ; α1-adrenergic receptors ; neurons ; cell culture ; WKY ; SH rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Neuronal cells from Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rat brains were established in culture to compare the expression of angiotensin II (Ang II) specific receptors and their regulation by norepinephrine (NE). Neurons from SH rat brains possess twice more Ang II specific receptors and expressed a proportional increase in Ang II stimulated [3H]-NE uptake compared with WKY neurons. NE caused a dose-dependent decrease in125I-Ang II binding in WKY neurons, an effect not observed when neurons from SH rat brains were incubated with NE. These observations suggest that the lack of NE-induced downregulation of Ang II receptors in neuronal cultures is genetically regulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228085
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of phorbol esters and a calcium ionophore on angiotensin II binding in rat brain synaptosomes (1989)
    Springer
    Neurochemical research 14 (1989), S. 25-30 
    Details
    ISSN: 1573-6903
    Keywords: Angiotensin II binding ; brain ; calcium ; phorbol esters ; synaptosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In previous studies we determined that protein kinase C (PKC) and calcium are important intracellular regulators of neuronal angiotensin II (Ang II) binding sites. In the present study we investigated the effects of the protein kinase C (PKC) agonist phorbol esters (PE) and also a calcium ionophore (A23187) on the specific binding of [125I]Ang II to brain synaptosomes prepared from rats of different ages. The rationale was to determine whether the larae changes in the level of brain Ang II specific binding observed in different age rats are due to changes in the regulation of these sites by PKC or by calcium. The present data indicate no qualitative differences in the effects of PE or A23187 on [125I]Ang II specific binding to hypothalamic or brain stem synaptosomes, from either 2–5 or 70-day-old rats, i.e. the active PE TPA increased while A23187 decreased Ang II binding in all situations. Thus, the dramatic differences in brain Ang II specific binding seen with age appear not to be due to changes in regulation by PKC or calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00969753
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  • 10
    Electronic Resource
    Electronic Resource
    Receptors for phorbol esters are primarily localized in neurons: Comparison of neuronal and glial cultures (1988)
    Springer
    Neurochemical research 13 (1988), S. 51-56 
    Details
    ISSN: 1573-6903
    Keywords: Neuronal cultures ; glial cultures ; protein kinase C ; phorbol ester receptor ; spontaneously hypertensive rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Binding of [3H]PDB has been measured in the present study to determine the levels of protein kinase C in the neuronal and astrocytic glial cells in culture from rat brain. Binding of [3H]PDB to homogenates of cultured neuronal cells from the brains of normotensive and hypertensive rats was time-dependent and specific. The relative potency for competition by various phorbol esters to [3H]PDB binding was TPA 〉 β-PDD 〉 POE 〉 α-PDD ≥4αphorbol. Scatchard analysis showed that neuronal cultures from normotensive rat brains contained 2–3 fold more phorbol ester receptors compared with the glial cultures from the same brains. No differences in theK d andB max were observed between neuronal cultures from normotensive and spontaneously hypertensive rat brains. These studies suggest that the phorbol ester receptors are primarily localized in neuronal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00971854
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