Radioligand-binding data

De Lean, A., Hancock, A. A. and Lefkowitz, R. J. (1982). Validation and statistical analysis of a computer modeling method for quantitative analysis of radioligand binding data for mixtures of pharmacological receptor subtypes, Mol. Pharmacol., 21, 5-16. 

FIGURE 4.12 Effect of alcuronium on the binding of [3H] methyl-QNB (filled circles) and [3H] atropine (open circles) on muscarinic receptors. Ordinates are percentage of initial radioligand binding. Alcuronium decreases the binding of [3H] methyl-QNB and increases the binding of [3H] atropine. Data redrawn from [7]. 

Among the biological assays, preference is given to assays that measure a direct interaction between a compound and a target, making data interpretation simpler. Therefore, radioligand binding assays and isolated enzyme assays are preferred to functional or cell-based assays. 

Figure 19.7 (top) illustrates competition binding data of two compounds that can compete for radioligands that label the receptor for the neurotransmitter dopamine (specifically, the Di receptor subclass). It can be seen that Compound A can eliminate specific binding at concentrations about 100-fold lower than required for Compound B. In toxicological (and pharmacological) terms, one would say that... 

Table 1 Radioligand binding test results at the p, 8, and k opioid receptors for selected experimental agents. H NMR data supplied by author...

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