Studies on the biochemical mode of action of EGYT-475, a new antidepressant.

We studied the mode of action of N-benzyl-piperazine-picolinylfumarate (EGYT-475) and of its metabolite N-benzyl-piperazine (EGYT-2760) in CFY rats. It was found that EGYT-475 had no uptake-inhibitory effect but EGYT-2760 inhibited the high-affinity uptake of 3H-noradrenaline, 3H-dopamine and especially that of 3H-serotonin both in vitro and ex vivo. Neither of the two compounds changed the serotonin turnover. Only EGYT-2760 evoked hyperthermia in rats at a high ambient temperature (28 degrees C). This effect was abolished by cyproheptadine but not by amitriptyline. EGYT-2760 antagonized serotonin-induced contractions of the stomach fundus but it was inactive in inhibiting the serotonin-induced platelet aggregation. Our results suggest that EGYT-2760, an active metabolite of EGYT-475, has a central serotoninomimetic action which involves 5-HT uptake-inhibition and 5-HT1 receptor agonistic effect.