(+)-AJ 76 and (+)-UH 232: central stimulants acting as preferential dopamine autoreceptor antagonists.
The biochemical and behavioral effects of the putative dopamine autoreceptor antagonists cis-(+)-5-methoxy-1-methyl-2-(n-propylamino)tetralin, (+)-AJ 76 and cis-(+)-5-methoxy-1-methyl-2-(di-n-propylamino)tetralin, (+)-UH 232, were evaluated in various in vivo models in rats. Both compounds produced a marked elevation in brain dopamine synthesis and turnover with only slight effects on the synthesis and turnover of serotonin (5-HT) and noradrenaline being noted. (+)-AJ 76 and (+)-UH 232 also failed to antagonize the decrease in cortical noradrenaline synthesis rate caused by the alpha 2 agonist clonidine. The apomorphine-induced decrease in dopamine synthesis rate in gamma-butyrolactone (GBL) treated animals was completely blocked by (+)-AJ 76 and (+)-UH 232 but not by d-amphetamine or methylphenidate. In activity experiments using habituated animals, (+)-AJ 76 and (+)-UH 232 produced locomotor stimulation and weak stereotypies and antagonized the sedative effects of low doses of apomorphine. Locomotor hyperactivity induced by apomorphine or the dopamine agonist DiPr-5,6-ADTN was antagonized by (+)-UH 232 and to a lesser degree by (+)-AJ 76. The locomotor hyperactivity produced by (+)-AJ 76, (+)-UH 232 and methylphenidate was completely prevented by reserpine pretreatment and partially blocked by the tyrosine hydroxylase inhibitor alpha-methyl-para-tyrosine (alpha-MT), whereas d-amphetamine-induced hyperactivity was only antagonized by alpha-MT pretreatment. It is concluded that (+)-AJ 76 and (+)-UH 232 produce behavioral stimulation via a preferential antagonism on central dopamine autoreceptors, an action different from that of all known stimulants including apomorphine, d-amphetamine and methylphenidate. (+)-AJ 76 and (+)-UH 232 possess but weak antagonistic effects on postsynaptic dopamine receptors and only the latter compound is able to induce sedation in rats.
D015107:4-Butyrolactone / Q000494:pharmacology; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000031:analogs & derivatives*; D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects* / Q000378:metabolism; D012110:Reserpine / Q000494:pharmacology; D013764:Tetrahydronaphthalenes / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D008781:Methyltyrosines; D009281:Naphthalenes; D018377:Neurotransmitter Agents; D011954:Receptors, Dopamine; D013764:Tetrahydronaphthalenes; C022260:alpha-methyltyrosine methyl ester; C015842:2-(N,N-dipropyl)amino-5,6-dihydroxytetralin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C051171:5-methoxy-1-methyl-2-(n-propylamino)tetralin; D012110:Reserpine; C045971:UH 232; D001058:Apomorphine; D015107:4-Butyrolactone