This study aimed to examine whether the increase in heart radioactivity levels after intravenous injection of 14C-tyramine to rats pretreated with the irreversible MAO inhibitor tranylcypromine could be antagonized by reboxetine, a potent and selective noradrenaline uptake blocker. Reboxetine was found totally to abolish the effect of tranylcypromine. Heart radioactivity levels after reboxetine and tranylcypromine were very similar to those found when tyramine was injected after reboxetine only. These results suggest that reboxetine might be advantageously combined with tranylcypromine, or any MAO inhibitor, in depressed patients unresponsive of either treatment given alone.