The effects of a 5-HT1 receptor ligand isapirone (TVX Q 7821) on 5-HT synthesis and the behavioural effects of 5-HT agonists in mice and rats.
The effects of 2-(4-(4-(2-pyrimidinyl)-1-piperazinyl)-butyl)-1,2-benzoisothiazol- 3(2H)one-1, 1-dioxide hydrochloride (isapirone, TVX Q 7821), a putative 5-HT1 receptor antagonist, has been studied on various models of 5-HT receptor sub-type function. In mice TVX Q 7821 produced a dose-dependent inhibition of the hypothermia induced by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) with an ED50 of 5.3 mg/kg suggesting that TVX Q 7821 was an antagonist of the presynaptic (possibly somato-dendritic) 5-HT1A receptor. TVX Q 7821 did not alter the locomotor response to the suggested 5-HT1B agonist RU 24969. The rate of mouse brain 5-HT synthesis was accelerated by TVX Q 7821 (10 mg/kg). 5-HT2 receptor-mediated head twitch behaviour induced by precursor loading with 5-HTP was unaffected by TVX Q 7821 (10 mg/kg) pretreatment 75 min earlier, but the head-twitch induced by the agonist 5-methoxy-N,N-dimethyltryptamine was enhanced by prior treatment with TVX Q 7821. In rats the hypothermia induced by 8-OH-DPAT was partially antagonised by TVX Q 7821 while the behavioural "serotonin syndrome" induced by 8-OH-DPAT (a possible post-synaptic 5-HT1B-mediated effect) was unaffected by TVX Q 7821 as was the locomotion induced by RU 24969. The data suggest that TVX Q 7821 is a good presynaptic 5-HT1A antagonist in mice, as indicated by the 8-OH-DPAT-induced hypothermia and 5-HT synthesis rate studies. It did not antagonise 5-HT1B-mediated behaviour in mice or rats and appeared to have an antagonist action at pre- but not post-synaptic 5-HT1A receptors in rats.
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004347:Drug Interactions; D007211:Indoles / Q000008:administration & dosage; D008297:Male; D008732:Methoxydimethyltryptamines / Q000008:administration & dosage; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects; D011743:Pyrimidines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D012701:Serotonin / Q000096:biosynthesis*; D013764:Tetrahydronaphthalenes / Q000008:administration & dosage
D007211:Indoles; D008732:Methoxydimethyltryptamines; D011743:Pyrimidines; D011954:Receptors, Dopamine; D013764:Tetrahydronaphthalenes; C025145:5-methoxy 3-(1,2,3,6-tetrahydro-4-pyridinyl)1H indole; D012701:Serotonin; C043077:ipsapirone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin