Tryptamine fingerprints in the classification of 5-hydroxytryptamine receptors
In a series of recent studies [1–4] we have investigated the utility of tryptamines in the classification of 5-hydroxytryptamine (5-HT) receptors. These studies have shown that in situations where conventional antagonists are unable to provide reliable quantitative information, ‘fingerprints’ comprising tryptamine affinity and relative efficacy estimates can improve the rigour with which 5-HT receptors are classified. A particular advantage of this approach is that it enables receptors to be identified positively. This is in contrast to the scheme proposed by Bradley et al.  in which, for example 5-HT1-like receptors are defined by a high agonist potency (≥5-HT) of 5-carboxamidotryptamine (5-CT), susceptibility to blockade by the nonselective antagonist methiothepin and a resistance to blockade by ketanserin and MDL 72222. In our view, application of such exclusion criteria establishes what the receptor is not rather than what it is.
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