The effect of chronic administration of trazodone on the acquisition of avoidance behavior in mice.

An atypical antidepressant trazodone, given in doses of 5 or 10 mg/kg ip during the period of avoidance training (15 min before the beginning of each of 5 consecutive daily sessions) significantly depressed the rate of acquisition of the conditioned avoidance response. However, in mice pretreated with trazodone, 10 mg/kg daily for the preceding 14 consecutive days, the treatment with 10 mg/kg before each session did not impair the acquisition of the conditioned avoidance response, and the treatment with a dose of 5 mg/kg improved the acquisition over the control level. The data show that the pattern of action of trazodone on the acquisition of conditioned avoidance response is the same as that of other antidepressant agents, desipramine and mianserin, and indicate that chronically administered antidepressant agents do not impair learning.