The reversible MAO inhibitor, brofaromine, inhibits serotonin uptake in vivo.
The inhibition of the binding of [3H]cyanoimipramine in the rat brain in vivo, with and without pretreatment with proadifen (SK & F 525 A) to prevent its metabolism, has recently been shown to reflect inhibition of 5-HT uptake. This method has been suggested to be more sensitive than other more indirect methods. We have used this method to study the reversible MAO-A inhibitor, brofaromine, which has been shown previously to inhibit 5-HT uptake into synaptosomal preparations in vitro and ex vivo at doses about 30 times higher than those that inhibited MAO-A, and a number of 5-HT uptake inhibitors. The effects of orally administered clomipramine, imipramine, citalopram, CGP 6085 A, fluoxetine and brofaromine on [3H]cyanoimipramine binding were similar to those obtained in the synaptosome ex vivo model in the absence of proadifen; ifoxetine seemed to be more potent in inhibiting [3H]cyanoimipramine binding. The effects of clomipramine, imipramine, citalopram and ifoxetine were moderately to markedly enhanced by proadifen, indicating a first-pass effect. The effect of brofaromine on [3H]cyanoimipramine binding showed a time course similar to that on MAO-A, and was not altered upon repeated treatment. The inactivity of another MAO-A inhibitor, moclobemide, suggest that the effect of brofaromine was due to true inhibition of 5-HT uptake and not to displacement of [3H]cyanoimipramine by elevated synaptic 5-HT. The possible role of inhibition of 5-HT uptake in the antidepressant effect of brofaromine is discussed.
Waldmeier
P C
PC
Research Department, Ciba-Giegy Ltd., Basel, Switzerland.
Stöcklin
K
K
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D007099:Imipramine / Q000031:analogs & derivatives / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology
D008996:Monoamine Oxidase Inhibitors; D010880:Piperidines; D012702:Serotonin Antagonists; C024316:cianopramine; D012701:Serotonin; C038213:brofaromine; D011335:Proadifen; D007099:Imipramine