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  • 1
    Electronic Resource
    Electronic Resource
    Selective visualization of rat brain 5-HT2A receptors by autoradiography with [3H]MDL 100,907 (1997)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 356 (1997), S. 446-454 
    Details
    ISSN: 1432-1912
    Keywords: Key words [3H]MDL100 ; 907 ; 5-HT2A receptors ; Rat brain ; Autoradiography ; in situ hybridization ; [3H]ketanserin ; [3H]mesulergine ; [3H]RP62203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The recently developed 5-HT2A receptor selective antagonist [3H]MDL100,907 ((+/–)2,3-dimethoxyphenyl-1-[2-(4-piperidine)-methanol]) has been characterized as a radioligand for the autoradiographic visualization of these receptors. [3H]MDL100,907 binding to rat brain tissue sections was saturable, had sub-nanomolar affinity (Kd=0.2–0.3nM), and presented a pharmacological profile consistent with its binding to 5-HT2A receptors (rank order of affinity for [3H]MDL100,907-labelled receptors: MDL100,907 〉 spiperone 〉 ketanserin 〉 mesulergine). The distribution of receptors labelled by [3H]MDL100,907 was compared to the autoradiographical patterns obtained with [3H]Ketanserin, [3H]Mesulergine, and [3H]RP62203 (N-[3-[4-(4-fluorophenyl)-piperazin-1-y1]propyl]-1,8-naphtalenesultam) and to the distribution of 5-HT2A receptor mRNA as determined by in situ hybridization. As opposed to the other radioligands, [3H]MDL100,907 labelled a single population of sites (5-HT2A receptors) and presented extremely low levels of non-specific binding. The close similarity of the distributions of [3H]MDL100,907-labelled receptors and 5-HT2A mRNA further supports the selectivity of this radioligand for 5-HT2A receptors and suggests a predominant somatodendritic localization of these receptors. The present results point to [3H]MDL100,907 as the ligand of choice for the autoradiographic visualization of 5-HT2A receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005075
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of functional responses in A9 cells transfected with cloned rat 5-HT1C receptors (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 347 (1993), S. 119-124 
    Details
    ISSN: 1432-1912
    Keywords: 5-HT1C receptors ; A9 cells potassium conductance ; Calcium response ; Fura-2/Fluo-3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Functional responses to stimulation of rat 5-HT1C receptors expressed in A9 cells were studied using whole cell voltage clamp and calcium recording techniques. Stimulation of 5-HT1C receptors evoked outward currents clamped at −50 mV. The outward currents were reduced when GTP was excluded from the intracellular recording solution or when GDR-β-S was added. 8-Bromo cyclic AMP (5 mmol/l) neither produced an effect per se nor affected the 5-HT-induced outward current in A9 cells, thus excluding CAMP as a second messenger involved in 5-HT1C receptor activation. Phorbol myristic acetate (PMA; 10 μmol/l) did not affect the electrical activity of the transfected A9 cells but reduced the 5-HT-induced current amplitude to 71±9% of the control value (n = 12). This indicates that activation of protein kinase C does not play a direct role in the 5-HT-induced response in these cells. The 5-HT induced currents mainly involved potassium ions, although a small contribution of chloride ions was also observed. The 5-HT-induced current was inhibited by the K+ channel blocking agents tetraethylammonium (1 mmol/l), apamin (0,5 μmol/l) and 4-aminopyridine (5 mmol/1). The 5-HT-induced currents recorded at −50 mV were unaffected by removal of extracellular calcium, but inclusion of the calcium chelator BAPTA (5 mmol/l) in the intracellular solutions abolished the current. Measurement with the calcium indicator Fluo-3 revealed a 5-HT-induced increase in intracellular calcium which was not affected by removal of extracellular calcium but declined after repeated stimulation. Determinated of pD2 and KB values of several 5-HT ligands using Fura-2 calcium measurements confirmed the pharmacology of the 5-HT1C receptor. The results show that cloned rat 5-HT1C C receptors expressed in A9 cells activate a calcium-dependent potassium conductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169255
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  • 3
    Electronic Resource
    Electronic Resource
    Calcineurin inhibits desensitization of cloned rat 5-HT1C receptors (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 348 (1993), S. 221-224 
    Details
    ISSN: 1432-1912
    Keywords: Rat 5-HT1C receptors ; A9 cells ; Desensitization ; Calcineurin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Functional responses to stimulation of rat 5-HT1C receptors expressed in A9 cells were studied using whole cell voltage clamp recording technique. Stimulation of 5-HT1C receptors with serotonin (5-HT) evoked calcium-dependent outward currents of 109 pA in cells clamped at — 50 mV. Pretreatment with the protein kinase C (PKC) activator phorbol myristic acetate (PMA) reduced the 5-HT-induced current amplitude by 46% of the control value. Inclusion of inositol triphosphate (IP3) in the pipette solution induced an outward current of 84 pA. The IP3-induced response was not affected by 60 min pretreatment with PMA. In the presence of the PKC antagonist calphostin C, 60 min treatment with PMA (10−6 mol/1) reduced the 5-HT response only by 8%. In cells preincubated with PMA, injection of the calcium/calmodulin dependent serine proteinphosphatase calcineurin gradually increased the 5-HT-induced responses by 34%. In A9 cells which were incubated 24 h with the 5-HT1C receptor agonist meta chlorophenylpiperazine hydrochloride (mCPP), 5-HT-induced responses were reduced by 23% of the vehicle pretreated control value. Injection of calcineurin in mCPP treated cells enhanced the 5-HT-induced response by 24%. The results suggest that in A9 cells rat 5-HT1C receptors are desensitized after phosphorylation by PKC. This desensitization can be counteracted by calcineurin-induced: dephosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169147
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