Comparison of desmethylsertraline with sertraline as a monoamine uptake inhibitor in vivo

1. Desmethylsertraline, a metabolite of the antidepressant drug sertraline, was compared with sertraline for its ability to produce effects characteristic of inhibitors of the serotonin transporter in vivo. Desmethylsertraline antagonized brain serotonin depletion by p-chloroamphetamine, a depletion dependent upon the serotonin transporter, being less potent than sertraline in rats but almost as potent as sertraline in mice. Desmethylsertraline was a weak antagonist of 6-hydroxydopamine-induced depletion of heart norepinephrine in mice; sertraline had no effect at the doses studied. 2. Desmethylsertraline decreased brain concentrations of 5-hydroxyindoleacetic acid (5HIAA) in rats as did sertraline, the duration of the effect after both drugs being at least 24 hrs but less than 48 hrs. 3. After sertraline injection, desmethylsertraline was present in rat brain at higher concentrations than the parent drug at 8 hrs and thereafter. 4. In rats, repeated injections of sertraline, at doses previously shown to diminish beta-adrenergic receptor-mediated responses, led to marked accumulation of desmethylsertraline in brain and to inhibition of the catecholamine transporters. 5. In mice, brain concentrations of desmethylsertraline were higher than those of parent drug within 7 hrs after sertraline injection and probably contributed importantly to the antagonism of p-chloroamphetamine effects. 6. These data show that desmethylsertraline is less potent than sertraline as a serotonin uptake inhibitor in vivo, as the in vitro data would have predicted, but that desmethylsertraline may nonetheless contribute to the prolonged inhibition of the serotonin transporter after sertraline administration, perhaps more in mice than in rats.