Elevated concentrations of CRF in the locus coeruleus of depressed subjects

In search of a depressed mouse: utility of models for studying depression-related behavior in genetically modified mice

The ability to modify mice genetically has been one of the major breakthroughs in modern medical science affecting every discipline including psychiatry. It is hoped that the application of such technologies will result in the identification of novel targets for the treatment of diseases such as depression and to gain a better understanding of the molecular pathophysiological mechanisms that are regulated by current clinically effective antidepressant medications. The advent of these tools has resulted in the need to adopt, refine and develop mouse-specific models for analyses of depression-like behavior or behavioral patterns modulated by antidepressants. In this review, we will focus on the utility of current models (eg forced swim test, tail suspension test, olfactory bulbectomy, learned helplessness, chronic mild stress, drug-withdrawal-induced anhedonia) and research strategies aimed at investigating novel targets relevant to depression in the mouse. We will focus on key questions that are considered relevant for examining the utility of such models. Further, we describe other avenues of research that may give clues as to whether indeed a genetically modified animal has alterations relevant to clinical depression. We suggest that it is prudent and most appropriate to use convergent tests that draw on different antidepressant-related endophenotypes, and complimentary physiological analyses in order to provide a program of information concerning whether a given phenotype is functionally relevant to depression-related pathology.

Importance of studying the contributions of early adverse experience to neurobiological findings in depression

Almost four decades of intensive research have sought to elucidate the neurobiological bases of depression. Epidemiological studies have revealed that both genetic and environmental factors contribute to the risk for depression. Adverse early-life experiences influence neurobiological systems within genetic limits, leading to the neurobiological and behavioral manifestations of depression. We summarize the burgeoning evidence concerning a pre-eminent role of early adverse experience in the pathogenesis of depression. The available data suggest that (1) early adverse experience contributes to the pathophysiology of depression, (2) there are neurobiologically different subtypes of depression depending on the presence or absence of early adverse experience, likely having confounded previous research on the neurobiology of depression, and (3) early adverse experience likely influences treatment response in depression. Classification of depression based on developmental and neurobiological features will likely considerably improve future research in the field of depression, and might lead to optimized treatment strategies that directly target different neurobiological pathways to depression.