Studies on the locus coeruleus system in an animal model for antidepressive activity.

The present study was performed in order to evaluate the role of brain noradrenergic system of the locus coeruleus (LC) in mediating the effect of desipramine (DMI) in the behavioral despair (immobility) induced by forced swim in rats. Both single and repetitive doses of DMI significantly reduced the immobility. The effect of single dose of drug was reduced in LC lesioned rats. On the other hand, lesions failed to influence the action of repetitive doses of DMI. A lesion of the LC alone failed to influence animals' behavior in the immobility test. Electrical stimulation of the LC (either unilateral or bilateral) significantly reduced the immobility i.e. produced an effect similar to that produced by DMI. The possible involvement of the LC in action of DMI and mechanisms of depression is discussed.