Effects of a new antidepressant drug on active avoidance behavior in rats. Comparative study with tricyclic antidepressants.

The effects of a new antidepressant drug, EGYT-475 (1-benzyl-4-(2'-pyridylcarbonyl)-piperazine) on the acquisition and extinction of conditioned avoidance behavior following short and long-term treatment were studied in rats. The effects were compared with those of amitriptyline, imipramine and desipramine. In a six-day acquisition period, EGYT-475 in a 200 mg/kg dose p.o facilitated the acquisition, while amitriptyline, imipramine and desipramine either had no effect or impaired the acquisition, depending upon the dose used. In a six-day extinction period, EGYT-475 delayed the extinction following either oral or intraperitoneal administration, while amitriptyline, imipramine, and desipramine in various doses facilitated the extinction. On prolonged treatment the delayed extinction was maintained even after 42 days in animals treated with EGYT-475. The results indicate that EGYT-475, in contrast to tricyclic antidepressants, does not impair the acquisition of avoidance conditioning but rather improves it while it does not facilitate the extinction of learned behavior but considerably delays it.