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  • 1
    Electronic Resource
    Electronic Resource
    In vivo labelling of pituitary dopamine D-2 receptors in the male rat using [3H]-raclopride (1989)
    Springer
    Journal of neural transmission 76 (1989), S. 13-28 
    Details
    ISSN: 1435-1463
    Keywords: Dopamine ; D-2 receptors ; in vivo binding ; 3H-raclopride ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The substituted benzamide drug [3H]-raclopride (Köhler et al., 1985) was used to label dopamine D-2 receptors within the individual lobes of the pituitary gland as well as in the brain of male rats in vivo. The in vivo [3H]-raclopride binding was found to be saturable, reversible and of high specificity. Between 5–30% of the binding was non-specific at saturating concentrations dependent upon the lobe of the pituitary gland as well as of the brain region (e.g., caudate nucleus and olfactory tubercle) studied. Saturation analyses revealed Bmax-values of 12.9±1.6 and 2.2±0.9pmol·g−1 wet weight in the intermediate and anterior lobes, respectively with respective KD values of 6.5±4.6 and 7.3±2.4 nmol·kg−1. Quantitative autoradiographic studies using a single concentration of [3H]-raclopride showed a similar relationship with regard to binding densities in the different lobes, and showed, in addition, that the posterior lobe contained the lowest number of specific [3H]-raclopride binding sites. The binding capacities and affinities of binding were 12.9±1.7 and 9.2±2.8 respectively in the caudate nucleus and 6.1±0.7 and 9.3±2.7 respectively in the olfactory tubercle. The pharmacological analysis revealed that (S)sulpiride, remoxipride and raclopride were 10 to 125 times more potent than their corresponding isomers [(R)sulpridie, FLA 731(−), and FLB 472, respectively] in blocking the in vivo [3H]raclopride binding in the pituitary gland as well as in brain. The in vivo potency of different D-2 antagonists in preventing the [3H]-raclopride binding in the anterior and intermediate lobes was: spiperone 〉 domperidone 〉 raclopride 〉 (S)sulpiride 〉 remoxipride. The D-1 selective antagonist SCH 23390 did not block the in vivo binding of [3H]-raclopride neither in the pituitary lobes nor in the brain. In agreement with these findings the D-2 agonists N,N-propylnorapomorphine and quinpirole (LY 171555) but not the D-1 agonist SKF 38393-A blocked the specific in vivo [3H]-raclopride binding in the pituitary gland as well as in the brain. Comparisons between the relative potencies of different drugs in blocking pituitary and brain D-2 receptors in vivo showed that some drugs, including sulpiride and domperidone, were more potent in the pituitary gland than in the brain, while remoxipride and raclopride were equipotent in the two areas. The D-2 agonists tested appeared to be slightly more potent in the brain than in the pituitary gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244988
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Regional distribution and in vivo binding of the atypical antipsychotic drug remoxipride. A biochemical and autoradiographic analysis in the rat brain (1992)
    Springer
    Journal of neural transmission 87 (1992), S. 49-62 
    Details
    ISSN: 1435-1463
    Keywords: Remoxipride ; dopamine ; drug distribution ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The regional brain distribution and binding of the antipsychotic benzamide drug remoxipride was studied in the male rat. After i.v. injections of3 H-remoxipride (1 μmol · kg−1) more than 85% of the radioactivity was identified as authentic remoxipride in brain by using reversed-phase liquid chromatography. Autoradiographic and spectroscopic analysis showed that3 H-remoxipride was distributed relatively even in different brain areas, with exception of the following structures, which showed highest drug concentrations: the choroid plexus, septum, medial part of the caudate nucleus, different areas of the thalamus and hypothalamus situated close to the cerebral ventricles. A closer analysis of the autoradiograms showed a gradient of radioactivity extending from the cerebral ventricles to the deeper parts of the brain at 30 minutes after injections. After 60 minutes radioactivity was detected throughout all forebrain dopamine receptive areas. These findings suggest that remoxipride enters the cerebrospinal fluid (CSF) via the vascular bed of the choroid plexus and that it enters the brain interstitial fluid from the CSF. In the caudate nucleus, nucleus accumbens, olfactory tubercle and olfactory bulb 30–40% of the radioactivity was reduced by pretreatment with the dopamine D-2 selective drug raclopride. In addition, small, but significant, reductions (10–15%) of3H-remoxipride derived radioactivity was found in the neocortex, hippocampus and the cerebellum, suggesting that remoxipride interacts with a D-2 receptor also in these cortical structures. Taken together, these studies show that after i.v. injections,3H-remoxipride enters the brain primarily in unmetabolized form when given in doses that affect DA receptor mediated behaviours, that it distributes to most areas throughout the neuraxis and that it binds to D-2 receptors in different parts of the basal ganglia, neocortex, hippocampus and cerebellum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01253110
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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