Animal models of depression

      While reading these two papers, I found I was most interested in the differing characterizations of what an animal model of depression looks like, and of how it should be evaluated. When I read the description of the numerous behavioral tests used in Bessa et al. I was immediately struck by how thoroughly they demonstrated that the symptoms experienced by the rats paralleled those seen in humans with depression. In other research papers I’ve read it has been clear that while some symptoms can be adequately mimicked in rats, often animal models of human diseases fall short of fully capturing the disorder. In fact, what seemed to define the conflicting conclusions set forth by these to papers was not a disagreement in the accuracy of data, but in the accuracy of what can be considered a measure of depression. Santarelli et al. based their conclusion on the assumption that NSF performance was sufficient to demonstrate that a rat is experiencing something comparable to depression seen in humans. Bessa et al., on the other hand, argued that NSF measures anxiety-like behaviors only, and while anxiety is correlated with depression, it cannot be used as a measure of depressive-like behaviors as a whole, or of how well an antidepressant is working. In my opinion, by widening the range of evaluations done to include the sucrose preference test to assess anhedonia and the forced swimming test to measure learned helplessness, Bessa et al. were able to define a stronger rat model of depression which encompassed symptoms that better mirror human experiences, and therefore reach a more accurate conclusion on the role neurogenesis plays in antidepressant effectiveness. Because of this major difference between the papers, both groups were able to prove the same point, that neurogenesis is essential for the anxiety-reducing behavioral effects of antidepressants, and yet come to opposite conclusions about what this means, a situation which I find fascinating and certainly worth remembering.