Effects of ORG 6582 on monoamine uptake in vitro

Fluoxetine at anorectic doses does not have properties of a dopamine uptake inhibitor

Although fluoxetine is a highly selective inhibitor of serotonin uptake in vitro and in vivo, some investigators have suggested that dopamine uptake inhibition may contribute to anorectic actions of fluoxetine. The present experiments were done to determine fluoxetine's effects in some animal protocols in which dopamine uptake inhibitors have characteristic actions. Mazindol prevented the depletion of striatal dopamine and its metabolites by amphetamine in iprindole-pretreated rats, but fluoxetine had no effect. Mazindol prevented the depletion of striatal dopamine and its metabolites by 6-hydroxydopamine injected intracerebroventricularly into rats, but fluoxetine had no effect. Mazindol enhanced the elevation of 3,4-dihydroxyphenylacetic acid concentration in rat brain after spiperone injection, but fluoxetine did not cause that effect. Fluoxetine did not mimic amfonelic acid in antagonizing the retention of alpha-methyl-m-tyramine invant striatum after the injection of alpha-methyl-m-tyrosine. These results show that fluoxetine, at doses that are effective in blocking the serotonin uptake carrier and causing anorexia, does not block the dopamine uptake carrier.

Single ion monitoring assay for the serotonin re-uptake blocker Org 6582 in plasma

An assay method has been developed to determine the serotonin re-uptake blocker Org 6582 as its free base in plasma. As internal standard an isomer of Org 6582 is used. The assay procedure includes protein precipitation by addition of trichloroacetic acid, n-hexane extraction from basic medium and derivatization with trifluoroacetic acid anhydride. Quantification is performed using gas chromatography mass spectrometry by monitoring the molecular ions of the N-trifluoroacetyl derivatives of Org 6582 and internal standard at m/z 315. The assay method was applied to plasma samples from toxicological and from Phase I clinical studies. The assay characteristics are discussed in relation to comparable assay methods routinely employed in the authors' laboratory to monitor drug levels.

On the role of 5-hydroxytryptamine in drug-induced antinociception

1. The effects of four specific inhibitors of 5-hydroxytryptamine (K-HT) uptake on morphine-, methadone- or pethidine-induced antinociception was studied in rats. Antinociception was assessed by means of hot plate (55 degrees C) reaction times. The effect of the compounds on the uptake of [3H]-5-HT into rat whole brain synaptosomes was also investigated. 2. Pretreatment with Org 6582, citalopram, zimelidine or femoxetine at doses devoid of antinociceptive activity potentiated morphine- but not methadone- or pethidine-induced antinociception. 3. A temporal correlation existed between the ability of Org 6582 to potentiate morphine-induced antinociception and to block synaptosomal [3H]-5-HT uptake. 4. 5-HT plays a critical role in the antinociceptive effect of morphine but not of methadone or pethidine.