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3H-(-)DO 710 discriminates guanine nucleotide sensitive and insensitive dopamine binding sites
Naunyn-Schmiedeberg'S Archives of Pharmacology
|May 1, 1985
Summary
Tritiated (-)DO 710 preferentially labels dopamine D-4 receptors in the striatum, distinguishing them from D-2 receptors. This radioligand aids in studying D-4 receptor pharmacology and distribution.
Area of Science:
- Neuroscience
- Pharmacology
- Receptor Binding Assays
Background:
- Dopamine receptors, specifically D-2 and D-4 subtypes, play crucial roles in neurological functions.
- Developing selective radioligands is essential for differentiating and characterizing these receptor subtypes.
- (-)DO 710 is a substituted benzamide derivative known to interact with both D-2 and D-4 dopamine binding sites.
Purpose of the Study:
- To tritiate (-)DO 710 for use as a radioligand to selectively label dopamine D-4 binding sites.
- To characterize the binding properties of 3H-(-)DO 710 in striatal tissue and compare it to D-2 receptors.
- To investigate the potential of 3H-(-)DO 710 to differentiate D-4 receptor pharmacology.
Main Methods:
- Tritiation of the substituted benzamide derivative (-)DO 710.
- In vitro receptor binding assays using 3H-(-)DO 710 on rat striatal and pituitary tissue.
- Saturation and competition binding experiments to determine affinity (Kd) and density (Bmax) of receptor sites.
- Evaluation of inhibition potencies of discriminant benzamide derivatives and classical neuroleptics.
Main Results:
- 3H-(-)DO 710 saturation curves in striatum indicated two binding sites with distinct affinities, corresponding to D-2 and D-4 receptors.
- Low concentrations (0.2 nM) of 3H-(-)DO 710 preferentially labeled the striatal D-4 site, as evidenced by discriminant benzamide derivative potencies.
- Agonist affinities for striatal sites labeled with 3H-(-)DO 710 differed from those at the pituitary D-2 receptor.
- In pituitary tissue (D-2 site only), 3H-(-)DO 710 exhibited low-affinity binding.
Conclusions:
- Tritiated (-)DO 710 serves as a valuable tool for differentially labeling dopamine D-4 receptors in the striatum.
- The radioligand allows for the study of D-4 receptor pharmacology, distinct from D-2 receptors.
- 3H-(-)DO 710 demonstrates utility in distinguishing between D-2 and D-4 receptor subtypes in specific brain regions.