Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Effects of Forskolin, Dibutyryl Cyclic AMP, and 5′N-Ethylcarboxamide Adenosine on 22Na Uptake by Rat Brain Synaptosomes Stimulated by Veratridine (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of forskolin, dibutyryl cyclic AMP, and 5′-N-ethylcarboxamide adenosine on specific 22Na uptake by synaptosomes stimulated by veratridine were investigated. All substances inhibited 22Na uptake, with forskolin more potent than 5′-N-ethylcarboxamide and this latter one more potent than dibutyryl cyclic AMP. In the absence of prein-cubation with forskolin, this substance caused little or no effect on 22Na uptake by synaptosomes. In the presence of the adenosine antagonist dipropylsulfophenylxanthine, the inhibitory effect of 5′-N-ethylcarboxamide adenosine on 22Na uptake was consistently antagonized. The results were interpreted as forskolin and 5′-N-ethylcarboxamide adenosine increasing cyclic AMP accumulation, and dibutyryl cyclic AMP mimicking it, and by these mechanisms decreasing sodium uptake through the sodium channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09358.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Excitatory and Inhibitory Effects of A1 and A2A Adenosine Receptor Activation on the Electrically Evoked [3H]Acetylcholine Release from Different Areas of the Rat Hippocampus (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The modulation by adenosine analogues and endogenous adenosine of the electrically evoked release of [3H]acetylcholine ([3H]ACh) was compared in subslices of the three areas of the rat hippocampus (CA1, CA3, and dentate gyrus). The mixed A1/A2 agonist 2-chloroadenosine (CADO; 2–10 µM) inhibited, in a concentration-dependent manner, the release of [3H]ACh from the three hippocampal areas, being more potent in the CA1 and CA3 areas than in the dentate gyrus. The inhibitory effect of CADO (5 µM) on [3H]ACh release was prevented by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 50 nM) in the three hippocampal areas and was converted in an excitatory effect in the CA3 and dentate gyrus areas. The A2A agonist CGS-21680 (30 nM) produced a greater increase of the evoked release of [3H]ACh in the CA3 than in the dentate gyrus areas, whereas no consistent effect was found in the CA1 area or in the whole hippocampal slice. The excitatory effect of CGS-21680 (30 nM) in the CA3 area was prevented by the adenosine receptor antagonist 3,7-dimethyl-1-propargylxanthine (10 µM). Both adenosine deaminase (2 U/ml) and DPCPX (250 nM) increased the evoked release of [3H]ACh in the CA1 and CA3 areas but not in the dentate gyrus. The amplitude of the effect of DPCPX and adenosine deaminase was similar in the CA1 area, but in the CA3 area DPCPX produced a greater effect than adenosine deaminase. It is concluded that the electrically evoked release of [3H]ACh in the three areas of the rat hippocampus can be differentially modulated by adenosine. In the CA1 area, only A1 inhibitory receptors modulate ACh release, whereas in the CA3 area, both A2A excitatory and A1 inhibitory adenosine receptors modulate ACh release. In the dentate gyrus, both A1 inhibitory and A2A excitatory adenosine receptors are present, but endogenous adenosine does not activate them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63010207.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ecto-5′-Nucleotidase Is Associated with Cholinergic Nerve Terminals in the Hippocampus but Not in the Cerebral Cortex of the Rat (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The extracellular catabolism of exogenously added AMP was studied in immunopurified cholinergic nerve terminals and in slices of the hippocampus and cerebral cortex of the rat. AMP (10 μM) was catabolized into adenosine and inosine in hippocampal cholinergic nerve terminals and in hippocampal slices, as well as in cortical slices. IMP formation from extracellular AMP was not detected. α,β-Methylene ADP (100 μM) inhibited almost completely the extracellular catabolism of AMP in these preparations. The relative rate of catabolism of AMP was greater in hippocampal slices than in cortical slices. AMP was virtually not catabolized when added to immunopurified cortical cholinergic nerve terminals, although ATP could be catabolized extracellularly under identical conditions. The comparison of the relative rates of catabolism of exogenously added AMP, calculated from the amount of AMP catabolized after 5 min, in hippocampal cholinergic nerve terminals and in hippocampal slices revealed a nearly 50-fold enrichment in the specific activity of ecto-5′-nucleotidase upon immunopurification of the cholinergic nerve terminals from the hippocampus. The results suggest that there is a regional variation in the subcellular distribution of ecto-5′-nucleotidase activity in the rat brain, the ecto-5′-nucleotidase in the hippocampus being closely associated with the cholinergic nerve terminals, whereas in the cerebral cortex ecto-5′-nucleotidase activity seems to be located preferentially outside the cholinergic nerve terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09420.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Solubilized Rat Brain Adenosine Receptors Have Two High-Affinity Binding Sites for l, 3-Dipropyl-8-Cyclopentylxanthine (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The specific binding of L-N6-[3H]phenylisopropyladenosine (L-[3H]PIA) to solubilized receptors from rat brain membranes was studied. The interaction of these receptors with relatively low concentrations of L-[3H]PIA (0.5–12.0 nA/) in the presence of Mg2+ showed the existence of two binding sites for this agonist, with respective dissociation constant (KD) values of 0.24 and 3.56 nM and respective receptor number (Bmax) values of 0.28 ± 0.03 and 0.66 ± 0.05 pmol/mg of protein. In the presence of GTP, the binding of L-[3H]PIA also showed two sites with KD values of 24.7 and 811.5 nM and Bmax values of 0.27 ± 0.09 and 0.93 ± 0.28 pmol/mg of protein for the first and the second binding site, respectively. Inhibition of specific L-[3H]PIA binding by 1, 3-dipropyl-8-cydopentylxanthine (DPCPX) (0.1–300 nM) performed with the same preparations revealed two DPCPX binding sites with Ki values of 0.29 and 13.5 nM, respectively. [3H]DPCPX saturation binding experiments also showed two binding sites with respective KD values of 0.81 and 10.7 nM and respective Bmax values of 0.19 ± 0.02 and 0.74 ± 0.06 pmol/mg of protein. The results suggest that solubilized membranes from rat brain possess two adenosine receptor subtypes: one of high affinity with characteristics of the A1 subtype and another with lower affinity with characteristics of the A3 subtype of adenosine receptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb08275.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    N6-Cyclohexyladenosine Inhibits Veratridine-Stimulated Na Uptake by Rat Brain Synaptosomes (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: The effect of the stable adenosine analogue, N6-cyclohexyladenosine, on 22Na uptake by rat brain synaptosomes stimulated by veratridine was investigated. In the presence of N6-cyclohexyladenosine, both the initial rate and the maximum sodium uptake were decreased. The inhibitory effect of N6-cyclohexyladenosine on sodium uptake by synaptosomes after 5 s of incubation with 22Na was concentration-dependent, antagonized by 1,3-dipropyl-8-p-sulfophenylxanthine, and attenuated by increasing the concentration of veratridine. The possibility that the adenosine analogue, by activating a xanthine-sensitive adenosine receptor, can operate inhibition of the voltage-dependent sodium channels is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb02997.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effect of Adenosine on 45Ca2+ Uptake by Electrically Stimulatad Rat Brain Synapatosomes (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effect of adenosine on 45Ca2+ uptake by rat brain synaptosomes stimulated by electrical pulses was investigated. 45Ca2+ uptake was voltage dependent. Adenosine (1 μM-1 μM) decreased the uptake of 45Ca2+ induced by electrical stimulation (amplitude, 20 V; duration, 400 pμs; frequency, 10 pulses/s) in a concentration-dependent manner. At a concentration of 1 μM, adenosine almost abolished the 45Ca2+ uptake induced by electrical stimulation (92.9 ± 5.3% inhibition), but when the calcium uptake was induced by high-K+ (60 mM) medium, the effect of adenosine (1 μM) was smaller (43.8 ± 5.2% inhibition). The inhibitory effect of 1 μM adenosine on calcium uptake induced by electrical stimulation was antagonized by 1,3-dipropyl-8-p-sulfophenylxanthine (5 μM). The possibility that adenosine interacts with the calcium channels opened by electrical stimulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb02079.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Parallel modification of adenosine extracellular metabolism and modulatory action in the hippocampus of aged rats (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 76 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The neuromodulator adenosine can be released as such, mainly activating inhibitory A1 receptors, or formed from released ATP, preferentially activating facilitatory A2A receptors. We tested if changes in extracellular adenosine metabolism paralleled changes in A1/A2A receptor neuromodulation in the aged rat hippocampus. The evoked release and extracellular catabolism of ATP were 49–55% lower in aged rats, but ecto-5′-nucleotidase activity, which forms adenosine, was 5-fold higher whereas adenosine uptake was decreased by 50% in aged rats. The evoked extracellular adenosine accumulation was 30% greater in aged rats and there was a greater contribution of the ecto-nucleotidase pathway and a lower contribution of adenosine transporters for extracellular adenosine formation in nerve terminals. Interestingly, a supramaximal concentration of an A1 receptor agonist, N6-cyclopentyladenosine (250 nm) was less efficient in inhibiting (17% in old versus 34% in young) and A2A receptor activation with 30 nm CGS21680 was more efficient in facilitating (63% in old versus no effect in young) acetylcholine release from hippocampal slices of aged compared with young rats. The parallel changes in the metabolic sources of extracellular adenosine and A1/A2A receptor neuromodulation in aged rats further strengthens the idea that different metabolic sources of extracellular adenosine are designed to preferentially activate different adenosine receptor subtypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00095.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    A2A Adenosine Receptor Facilitation of Neuromuscular Transmission (2000)
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The influence of stimulus pulse duration on calcium mobilization triggering facilitation of evoked [3H]acetylcholine ([3H]ACh) release by the A2A adenosine receptor agonist CGS 21680C was studied in the rat phrenic nerve-hemidiaphragm. The P-type calcium channel blocker ω-agatoxin IVA (100 nM) decreased [3H]ACh release evoked with pulses of 0.04-ms duration, whereas nifedipine (1 μM) inhibited transmitter release with pulses of 1-ms duration. Depletion of intracellular calcium stores by thapsigargin (2 μM) decreased [3H]ACh release evoked by pulses of 1 ms, an effect observed even in the absence of extracellular calcium. With short (0.04-ms) stimulation pulses, when P-type calcium influx triggered transmitter release, facilitation of [3H]ACh release by CGS 21680C (3 nM) was attenuated by both thapsigargin (2 μM) and nifedipine (1 μM). With longer stimuli (1 ms), a situation in which both thapsigargin-sensitive internal stores and L-type channels are involved in ACh release, pretreatment with either ω-agatoxin IVA (100 nM) or nifedipine (1 μM) reduced the facilitatory effect of CGS 21680C (3 nM). The results suggest that A2A receptor activation facilitates ACh release from motor nerve endings through alternatively mobilizing the available calcium pools (thapsigargin-sensitive internal stores and/or P- or L-type channels) that are not committed to the release process in each stimulation condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.0742462.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Immunologically Distinct Isoforms of Ecto-5′-Nucleotidase in Nerve Terminals of Different Areas of the Rat Hippocampus (2000)
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Ecto-5′-nucleotidase is regarded as being the key enzyme in the formation of the neuromodulator adenosine from released ATP. However, the association of ecto-5′-nucleotidase with nerve terminals is not consensual. Only enzyme histochemical and biochemical studies, but not immunocytochemical studies, agree on a general synaptic location of the enzyme. To clarify this issue further we tested the effect of an antibody against ecto-5′-nucleotidase, previously used in immunocyto-chemical studies, on the activity of ecto-5′-nucleotidase in fractions of nerve terminals isolated from different areas of rat hippocampus. The specific activity of extracellular AMP catabolism was higher in synaptosomes from the CA3 area (0.81 ± 0.06 nmol/min/mg of protein) than from synaptosomes from the CA1 area or the dentate gyrus or from the whole hippocampus (0.49-0.68 nmol/min/mg of protein). The catabolism of AMP (10 μM) was equally inhibited (85-92%) in synaptosomes from whole hippocampus, CA1, CA3, or dentate gyrus by α,β-methylene-ADP (100 μM) and equally unaffected by p-nitrophenyl phosphate (0.5 mM) or rabbit IgGs (100 μg/ml). However, the antiserum against ecto-5′-nucleotidase (100 μg/ml) inhibited extracellular AMP catabolism by 44% in CA3 synaptosomes but had little or no effect in synaptosomes from CA1, dentate gyrus, or whole hippocampus. A similar difference in the inhibitory potential of the antibody was observed between fractions of isolated 5′-nucleotidase binding to concanavalin A-Sepharose (70%) and fractions not retained by the lectin column (18%). Taken together, these results suggest that immunological isoforms of ecto-5′-nucleotidase exist in the rat hippocampal nerve terminals, with predominance in the CA3 area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.0740334.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Increase in the Number, G Protein Coupling, and Efficiency of Facilitatory Adenosine A2A Receptors in the Limbic Cortex, but not Striatum, of Aged Rats (1999)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 73 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : Adenosine's effects result from a balanced activation of inhibitory A1 and facilitatory A2A receptors. Because in aged animals there is an increased number of A2A receptors, we now compared the efficiency of A2A receptors in cortical and striatal preparations of young adult (6-week-old) and aged (2-year-old) rats. In cortical, in contrast to striatal, membranes from aged rats, A2A receptors were more tightly coupled to G proteins, because 5′-guanylylimidodiphosphate (100 μM) increased by 321% the Ki of the A2A agonist CGS21680 as a displacer of binding of the A2A antagonist [3H]ZM241385 (1 nM), compared with a 112% increase in young rats. In cortical slices, CGS21680 (30-1,000 nM) was virtually devoid of effect on cyclic AMP accumulation in young rats but increased cyclic AMP accumulation with an EC50 of 153 nM in aged rats, whereas the efficiency of CGS21680 was similar in striatal slices of young and aged rats. CGS21680 (30 nM) was virtually devoid of effect on acetylcholine release from hippocampal CA1 slices of young rats but caused a 55% facilitation in aged rats. These results show that the number of A2A receptors, their coupling to G proteins, and their efficiency are enhanced in the limbic cortex of aged rats, suggesting a greater involvement of facilitation in adenosine responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.731733.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...