Synthesis and Pharmacological Evaluation of 1-Phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes as Ligands for a Novel Receptor with σ-like Neuromodulatory Activity

Certainnovel 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (1-phenyl-3-aminotetralins, PATs) produced stimulation (ca. 30% above basal levels) of tyrosine hydroxylase (TH) activity at 0.1 µM concentrations in rodent brain tissue. This effect on TH was blocked by the putative σ-receptor antagonist BMY-14802, suggesting involvement of a novel neuromodulatory σ-like receptor. Within the new phenylaminotetralin series, a correlation was found between the ability to stimulate TH and the potency to compete for binding sites labeled by (±)-[³H]1-phenyl-3-(N,N-dimethylamino)-6-chloro-7-hydroxy-1,2,3,4-tetrahydronaphthalene {[³H](±)-4}. trans-Catechol analogs had low affinity for [³H]4 sites, and although they inhibited TH activity, this effect was not blocked by known σ or dopamine antagonists. Analogs with dihydroxy substituents (catechols), as well as nitrogen substituents larger than methyl, had little affinity for [³H]4 binding sites and did not significantly affect TH activity. The pharmacology of the [³H]4 binding site is unique from that of any known σ or dopamine receptor, thus the effects appear to be mediated by a previously uncharacterized binding site/receptor. The site has stereoselectivity for the (1R,3S)-(−)-isomer of 1-phenyl-3-(N,N-dimethylamino)-1,2,3,4-tetrahydronaphthalene; this isomer is also more active at stimulating TH. Thus, certain 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes appear to be selective probes of a novel receptor type that mediates σ-like neuromodulatory activity and may have pharmacotherapeutic utility in conditions in which modulation of dopamine function is important.