DIZOCILPINE ANTAGONIZES THE EFFECT OF CHRONIC IMIPRAMINE ON LEARNED HELPLESSNESS IN RATS

Dizocilpine coadministered with imipramine (IMI) through an SC-implant ed osmotic minipump completely prevents the occurrence of behavioral s upersensitivity to quinpirole, as well as the decrease of dopamine D-1 and P-adrenergic receptor function. The present report shows that, in the same experimental conditions, dizocilpine completely antagonized the capacity of IMI to prevent the development of the learned helpless ness behavior in rats. Thus suggesting that the blockade of NMDA recep tors also antagonizes the antidepressant effect of IMI. Interestingly, rats acutely treated with dizocilpine 30 min before the inescapable s hock session behaved similarly to naive animals during the escape test session.