The paper presents the results of studies into the effects of single and repeated (2 or 10 mg/kg po, twice daily for 14 days) administration of imipramine (IMI) on the behavior of male Wistar rats in an acoustic startle response test. Statistically significant attenuation of the animal reactivity was observed after 8 or 14 days administration of IMI in a dose of 10 mg/kg. Apomorphine APO (1.0 mg/kg, ip) enhanced the animals reactivity after repeated (but not single) administration of IMI in a dose of 2 mg/kg. The obtained results confirm the hypothesis about an increase of the dopaminergic system reactivity under the influence of repeated administration of tricyclic antidepressants.