Pargyline conjugate-induced long-term activation of monoamine oxidase as an immunological model for depression.

We describe an animal model of long-term depression based on active immunization of albino rats against BSA-conjugated inhibitor of monoamine oxidase, antidepressant, pargyline. Immunization resulted in anti-pargyline antibody formation and significant activation of monoamine oxidase A in brain. Immunized rats demonstrated potent decrease of motor, orientation and exploratory activity, increase of the immobility time ("despair") in Porsolt test, as well as notable signs of fear and anxiety in elevated plus maze. The cognitive processes were not significantly affected: the speed of learning with negative and positive reinforcement was not diminished. Complex effect on craving for alcohol (long-term suppression after short-term increase) was also demonstrated. The long-term (more than 45 days) depression achieved in this model makes it potentially important tool for testing new antidepressant pharmaceuticals.