title: Biochemical evidence for the 5-HT agonist properties of PAT (8-hydroxy-2-(di-n-propylamino)tetralin) in the rat brain.
abstract: In vitro investigations revealed that PAT (8-hydroxy-2-(n-dipropylamino)tetralin) interacted with postsynaptic 5-HT receptors in the rat brain: the drug stimulated 5-HT-sensitive adenylate cyclase in homogenates of colliculi from new-born rats (KAapp 8.6 microM) and inhibited the specific binding of [3H]5-HT to 5-HT1 sites. The PAT-induced inhibition of [3H]5-HT binding showed marked regional differences compatible with a preferential interaction of PAT (IC50 2 nM) with the 5-HT1A subclass. As previously seen with 5-HT agonists, the efficacy of PAT for displacing [3H]5-HT bound to hippocampal membranes was markedly increased by Mn2+ (1 mM) and reduced by GTP (0.1 mM). PAT also affected presynaptic 5-HT metabolism since it inhibited competitively (Ki 1.4 microM) [3H]5-HT uptake into cortical synaptosomes and reduced (in the presence of the 5-HT uptake inhibitor fluoxetine) the K+-evoked release of [3H]5-HT previously taken up or newly synthesized from [3H]tryptophan in cortical or striatal slices. This latter effect was prevented by 5-HT antagonists (methiothepin, metergoline) suggesting that it was mediated by the stimulation of presynaptic 5-HT autoreceptors by PAT. Like 5-HT, PAT counteracted the stimulatory effect of K+-induced depolarization on the synthesis of [3H]5-HT from [3H]tryptophan in cortical slices. It is concluded that PAT is a potent 5-HT agonist acting on both post- and presynaptic 5-HT receptors in the rat brain.
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology; D001923:Brain Chemistry / Q000187:drug effects*; D002540:Cerebral Cortex / Q000378:metabolism; D005260:Female; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D008566:Membranes / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000502:physiology*; D013134:Spiperone / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014365:Tryptophan Hydroxylase / Q000378:metabolism
chemical_list: D009281:Naphthalenes; D011954:Receptors, Dopamine; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D012701:Serotonin; D013134:Spiperone; D006897:Hydroxyindoleacetic Acid; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D014365:Tryptophan Hydroxylase; D000262:Adenylyl Cyclases