Quantitative assessment of heterogeneous 3H-spiperone binding to rat neostriatum and frontal cortex |
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Authors: | D.R. Howlett S.R. Nahorski |
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Affiliation: | Department of Pharmacology and Therapeutics, Medical Sciences Building, University of Leicester, University Road, Leicester. LE1 7RH. U.K. |
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Abstract: | Anomalies of the binding of 3Hspiperone to rat cerebral membranes have been examined. By employing a very low ligand concentration () we have demonstrated that even within the corpus striatum, 3Hspiperone appears to bind to multiple sites and that dopaminergic and serotonergic agents can selectively inhibit from these sites. In the corpus striatum, 75–80% of the 3Hspiperone specific binding can be inhibited with high affinity by dopaminergic drugs while some 20–30% is inhibited with high affinity by serotonergic compounds. The two 3Hspiperone sites, which we have shown to have affinities of 31 and 325 pM, may therefore represent dopaminergic and serotonergic sites. At higher concentrations of 3Hspiperone, however, the picture may be complicated by a further low affinity site. The great selectivity shown by dopaminergic agonists for the two 3Hspiperone sites explains the ‘flattened’ displacement curves reported for 3Hspiperone/agonist interactions. As dopaminergic agents show the greater affinity for the high affinity 3Hspiperone site, it is tempting to speculate that this site has the greatest association with the dopamine receptor. |
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