Effects of age on susceptibility to the induction of depressive behavior and imipramine in rats

Effects of age on depression vulnerability and antidepressant efficacy remain an important concern. Here, we show, by using a novel animal model of depressive behavior, that young rats (4 weeks old) are more vulnerable to the induction of depressive behavior than older ones (3, 6, and 14 months old). The induced depressive behavior in different ages of rats, however, was similarly sensitive to imipramine. A direct cerebroventricular administration of brain-derived neurotrophic factor was also sufficient to produce an antidepressant-like effect in the rats of different ages. These results suggest that although different ages of rats exhibit different sensitivity to the induction of depressive behavior, the induced depressive behavior may involve the same type of underlying abnormal neuropathophysiology in the brain and is sensitive to imipramine and brain-derived neurotrophic factor treatment. Behavioural Pharmacology 19:334-338 (c) 2008 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.