1-(2-pyrimidinyl)-piperazine may alter the effects of the 5-HT1A agonist in the learned helplessness paradigm in rats.
The 5-HT1A agonists buspirone, gepirone and ipsapirone have been shown to possess antidepressive-like properties in several animal models of depression as well as in clinical studies. These compounds are metabolized to 1-(2-pyrimidinyl)-piperazine (1-PP) in rats and humans. In the learned helplessness paradigm, buspirone exhibits a biphasic action: at low or moderate doses it shows an antidepressant-like effect but this action progressively disappears as the doses are increased. In order to establish whether 1-PP affects the reversal of helpless behaviour induced by the 5-HT1A agonists at high doses in rats, we have investigated its role in the learned helplessness. Thus, 1-PP has been evaluated alone (0.06-4 mg/kg/day) or in combination with a selective 5-HT1A agonist 8-OH-DPAT (0.25 mg/kg/day) which is not metabolized to 1-PP and buspirone (0.5 mg/kg/day). In addition, buspirone at a higher dose (2 mg/kg/day) has also been examined in the presence of proadifen which inhibits oxidative metabolism. Our results show that i) daily injections of 1-PP did not reverse helpless behaviour, ii) the reversal of helpless behaviour by 8-OH-DPAT or active dose of buspirone was antagonized by daily coadministration of 1-PP, iii) in rats pretreated with proadifen, the highest "inactive" dose of buspirone induces a reversal of helpless behaviour. These results strongly suggest that up to a certain concentration 1-PP can impair the effects of the parent drug in the learned helplessness.
Départment de Pharmacologie, Faculté de Médecine Pitié-Salpêtrière, Paris, France.
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects; D002065:Buspirone / Q000031:analogs & derivatives* / Q000494:pharmacology; D004597:Electroshock; D006380:Helplessness, Learned; D008297:Male; D010084:Oxidation-Reduction; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology
D014151:Anti-Anxiety Agents; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D011335:Proadifen; C037921:1-(2-pyrimidinyl)piperazine; D002065:Buspirone