Benjamin, L.C.; Young, Lauriann E.; Young, Ronald E
Author Affiliation, Ana.
Department of Basic Medical Sciences
Dopaminergic lesioning of the nucleus accumbens potentiates learned helplessness
Alzheimer's Disease Review
Date of Publication
'Learned helplessness' is an experimental model of depression in which repeated inescapable shock induces a state of helplessness. The response seen is conditioned freezing in which the animal is immobile. Much research focuses on the role of serotonin or norepinephrine in the aetiology of depression, whereas the literature is sparse on the role of dopamine (DA). The mesolimbic system is intimately concerned with emotional expression and its nucleus accumbens septi (NAS) has been the focus of research on motivational behavior. The study was therefore designed to evaluate the influence of the dopaminergic (DAergic) mesolimbic system on learned helplessness. Rats were either sham-lesioned or lesioned with 6-hydroxydopamine at the level of the NAS. They were confined singly to one arm of a Y-maze and exposed to electric foot-shock. Freezing response, an index of learned helplessness, and exploratory behaviour in the maze, were assessed at 24 hours (Trial 1) and 2 weeks (Trial 2) post-training. The results indicated that DA depletion in the NAS, increased conditioned freezing. These findings may have clinical implications regarding the use of DA in the pharmacotherapy of depressive disorders either alone or in co-morbid conditions such as Alzheimer's disease.....