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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Neurotensin (NT) is now reasonably well established as a neurotransmitter or neuromodulator candidate in the CNS. In the present study, we characterized the NT receptors in dispersed cells from the anterior lobe of rat pituitary and investigated the involvement of both cyclic AMP and calcium in the release of prolactin (PRL) induced by NT receptor stimulation. The [3H]NT binding to membranes from anterior pituitary dispersed cells was found saturable and stereospecific. Scatchard analysis of the data gave a straight line indicating a Bmax value of 121 ± 11 fmol/mg protein and a KD value of 1.4 ± 0.2 nM. The calculated IC50 values for [3H]NT binding were 5.8 nM for NT, 7.8 nM for L-Phe-NT, and 3,000 nM for the pharmacologically inactive form D-Phe-NT. NT, up to a concentration of 1 μM, did not affect the cyclic AMP generating system in homogenates of anterior pituitary from male or lactating female rats. The same pattern of results was obtained for cyclic AMP formation in intact cells. NT and its analogs stereospecifically enhanced the influx of calcium into dispersed cells from rat anterior pituitary. The effect was time- and dose-dependent. It appeared to be associated with neurotransmitter-operated calcium channels since: (1) preincubation of the cells with tetrodotoxin did not affect the increase in calcium influx induced by NT; (2) concentrations of verapamil that counteract the influx of calcium induced by potassium lacked the capacity to modify the influx of calcium induced by NT; and (3) NT lost its capacity to release PRL in the absence of extracellular calcium. The significant correlation of the effective concentrations of NT and its analogs for binding and biological activities indicates that occupancy of NT receptors in anterior pituitary modifies calcium channel permeability of the cell membranes, resulting in an accumulation of intracellular calcium that participates in the cascade of events that are ultimately expressed as an enhanced release of PRL.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The present study demonstrates that 3,4-dihydroxyphenylethylamine (DA, dopamine) prevents neurotensin (NT) stimulation of both prolactin (PRL) release and calcium influx by interacting with specific receptors that are functionally linked to calcium channels. As shown by the studies with dispersed cells from rat anterior pituitary, the pharmacology of the control of PRL release and calcium influx, both induced by NT, was found to be typical of a DAergic process. This was demonstrated (1) by the order of potency of agonists in inhibiting PRL release and calcium influx (DA 〉 epinephrine 〉 norepinephrine isoproterenol); (2) by the high affinity of antagonists such as haloperidol and fluphenazine for this process; and (3) by the high degree of stereoselectivity of sulphide. Specific D2 receptor agonists, such as bromocriptine and lisuride, and the specific D2 receptor antagonist (-)-sulpiride were found to be highly potent on the DA receptors negatively coupled with calcium channels and PRL release. DA was found to lack the capacity to change the influx of calcium induced by either the sodium channel activator veratridine or high extracellular potassium levels, thus indicating a specific action of this amine on calcium channels sensitive to NT. In a range of concentrations that are effective in inhibiting either the calcium influx or the PRL release, both induced by NT, DA did not alter the cyclic AMP generating system. DA (from 1.0 nM to 50 nM) did not affect adenylate cyclase activity in rat pituitary gland homogenates and did not modify intracellular cyclic AMP levels in pituitary cells. The putative correlation between DA suppressing activity of the NT effects and the adenylate cyclase system was verified in pertussis toxin-treated pituitary cells. At the time that DA receptors negatively coupled to inhibition of adenylate cyclase were not operative, DA was still fully effective in preventing NT stimulation of PRL release. The lack of effect of low concentrations of DA on both basal adenylate cyclase activity and cyclic AMP content in pituitary cells, together with their capacity to inhibit the NT effects in pertussis toxin-treated cells, suggest that DA may act independently of cyclic AMP in the control of PRL secretion. These observations lead to the hypothesis of the existence of two inhibitory mechanisms for DA in mammotrophs.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mechanisms of Ageing and Development 12 (1980), S. 39-46 
    ISSN: 0047-6374
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0167-0115
    Keywords: Angiotensin II ; Cyclic AMP ; Glomerulosa cell
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 73 (1995), S. 151-151 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Regulatory Peptides 10 (1985), S. 203-208 
    ISSN: 0167-0115
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1041
    Keywords: aldosterone ; DA2-receptor ; co-dergocrine ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In this study we have investigated the effect of co-dergocrine, a selective DA2-agonist, on plasma aldosterone concentrations (PAC) in twelve patients with essential hypertension both in basal conditions and during sodium depletion. Sodium depletion resulted in an increase of PAC from 38 (13) pg/ml to 297 (21) pg/ml. The PAC response to sodium depletion was reduced to 155 (29) pg/ml by co-dergocrine. No significant PAC changes were found in patients maintained on a normal sodium intake. In addition the drug did not significantly modify plasma renin activity (PRA) in either experimental group. These results suggest that the dopaminergic inhibition of aldosterone secretion in man is mediated by DA2-receptors in the adrenal cortex.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: co-dergocrine ; sulpiride ; hypertension ; DA-2 receptors ; dopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of the study was to define the role of peripheral dopaminergic mechanisms in the regulation of blood pressure. The data suggest that the hypotensive effect of the dopaminergic agonist co-dergocrine in elderly hypertensive patients is mediated by interaction with peripheral DA-2 receptors, since it was reversed by the selective antagonist sulpiride in a dose that does not significantly cross the blood brain barrier. The findings suggest the possible therapeutic use of dopamine DA-2 agonists in elderly hypertensive patients.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 19 (2000), S. 253-261 
    ISSN: 1438-2199
    Keywords: Keywords: Amino acids ; Cerebellar neurons ; Cyclin-dependent kinase ; Excitotoxicity ; Glutamate ; Neurodegenerative diseases ; Tumour suppressor gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Fifteen minute exposure of primary cultures of cerebellar granule cells to micromolar concentrations of glutamate results in apoptotic cell death. Among the intracellular events triggered by glutamate, we identified two transcriptional factors, i.e. the p50 member of the NF-κB family and the tumor suppressor phosphoprotein p53, that are apparently linked by a sequential trascriptional program. We found that pretreatment of the cultures with aspirin (ASA), which inhibits NF-κB activation, resulted in a complete prevention of glutamate-induced p53 immunoreactivity. The same results were obtained pretreating the cells with a specific p53 antisense oligonucleotide. Both ASA and p53 antisense abolished glutamate-induced apoptosis. We also found that two other proteins, the cyclin dependent kinase inhibitor p21 and DNA mismatches repair MSH2, whose encoding genes are well known target of p53, were upregulated by glutamate. On these bases, we propose NF-κB, p53, p21 and MSH2 as relevant contributors of the glutamate-induced pro-apoptotic pathway.
    Type of Medium: Electronic Resource
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