The “Learned Helplessness” Model in Rats: Possibilities and Limitations in Assessing a Depressive-Like State and Effects of Antidepressants

The “learned helplessness” (LH) model in rats is widely used in a battery of tests to assess depression-like behaviour and the effects of antidepressants. The model is considered to be suffi ciently valid, though having some limitations with reproducibility. This review discusses the possibilities of using the model for assessing the symptoms of a depressive-like state and the pathogenesis of depression, as well as the effects of antidepressants. The factors affecting the reproducibility of the LH model are described, the most important of which is the different sensitivity of animals to stress. Several protocols for the induction and testing of LH, which are used by different research teams, are presented. Due to the diffi culty of comparing the results obtained using different LH protocols, LH models should be standardized for use in individual laboratories. LH models are worth using in preclinical studies of potential drugs exhibiting antidepressant activity.

Assessing the relationship between the human learned helplessness depression model and anhedonia

The learned helplessness (LH) model is one of the most commonly used acute stress models to explain depression and it has shown good face and predictive validity. However, despite being able to induce depressed-like behaviors and corresponding psychophysiological changes, there is little evidence showing that the LH paradigm can produce anhedonia, a core symptom seen in all forms of depression in humans. So far a couple of studies showed that rodents bred for helplessness develop anhedonic-like behaviors in response to stress; yet, to the best of our knowledge, no similar human research has tried to investigate the direct relationship between the LH model and anhedonia. In the present study, we use a modified version of the original LH task to experimentally and temporarily induce learned helplessness in college students and then examine if the human LH paradigm induces anhedonia. We aim to 1: address the ill-defined connection between the LH model and anhedonia, and 2: directly assess helplessness in humans as opposed to the majority of non-human animal subjects used in the helplessness literature. We believe that our study will fill an important gap in the learned helplessness model literature, and will advance our understanding of the relationship between depression and perceived control, as well as place limitations to what can and cannot be inferred from non-human animal data in this topic.

Animal Models in Psychiatry

Darwin made a compelling case that studies of animals could provide insights into the behavior of humans. Early studies by Pavlov and Harlow paved the way for further developments of animal models of psychiatric disorders. Seligman and Maier’s learned helplessness model continues to be employed in laboratory studies of stress and depression. It has become clear that no single animal model can possibly reproduce all of the critical facets of a mental disorder in humans. However, animal models do provide an essential element in attempts to understand the mechanisms that underlie mental disorders and to reveal molecular targets for the development of new drug therapies. Concerns have been raised about the reproducibility of laboratory experiments with inbred strains of laboratory mice and rats. Any animal model should be evaluated based upon a battery of behavioral tests and the parameters of stressful stimulation employed in experiments should be chosen with care.