Utilization of Diurnal Rodents in the Research of Depression

Abstract

Preclinical Research Most neuropsychiatric research, including that related to the circadian system, is performed using nocturnal animals, mainly laboratory mice and rats. Mood disorders are known to be associated with circadian rhythm abnormalities, but the mechanisms by which circadian rhythm disruptions interact with depression remain unclear. As the circadian system of diurnal and nocturnal mammals differs, we previously suggested that the utilization of diurnal animal models may be advantageous for understanding these relations. During the last 10 years, we and others established the validity of several diurnal rodent species as a model for the interactions between circadian rhythms and depression. Diurnal rodents respond to photoperiod manipulation in a similar way to humans, the behavioral outcome is directly related to the circadian system, and treatment that is effective in patients is also effective in the model. Moreover, less effective treatments in patients are also less effective in the model. We, therefore, suggest that using diurnal animal models to study circadian rhythms-related affective disorders, such as depression, will provide new insights that will hopefully lead to the development of more effective treatments. Drug Dev Res 77 : 347-356, 2016. © 2016 Wiley Periodicals, Inc.

The Circadian Syndrome: is the Metabolic Syndrome and much more!

“…Herein we discuss research findings relating to the proposed Circadian Syndrome risk components and comorbidities (Table 2). Hypertension Lack of nocturnal decline in blood pressure [30,62] High blood pressure [22] Lipids Disrupted lipid homeostasis [69,70] Obesity Disrupted diurnal rhythms in the white adipose tissue transcriptome [73] Obesity [22] Blood glucose levels Disrupted daily rhythms in blood glucose levels and glucose intolerance [17,21,75] Disrupted daily rhythms in blood glucose levels and glucose intolerance [22] Fatty liver Disrupted triglyceride accumulation, inflammation, oxidative stress and mitochondrial dysfunction [29] Depression Circadian disruption increases the incidences of depression [86,87] Circadian disruption increases the incidences of depression [22,83,84,[105][106][107][108][109][110] Sleep disturbances Circadian disturbances result in sleep loss and mistimed sleep [56,97] Proposing a Circadian Syndrome: Cardiovascular-related components Circadian oscillations have been reported for both physiological CVD regulation including heart rate and blood pressure [57], for cardiac disorders including arrythmias [58,59], and there is circadian variation in frequency of onset of myocardial infarction and sudden cardiac death [19,60].…”

“…Depression is a well-established comorbidity associated with T2DM [79][80][81][82]. Nearly all patients with affective disorders including depression show significant disruptions in circadian rhythms [83][84][85][86][87].…”

“…Depression is a well‐established comorbidity associated with T2DM . Nearly all patients with affective disorders including depression show significant disruptions in circadian rhythms . Depression is related to disturbances of the circadian clock, and light therapy and other treatment affecting the circadian clock are used as a therapy for depression .…”

Animal models for bipolar disorder: from bedside to the cage

“…Here it is to consider that the manipulations have been mainly conducted in nocturnal animals and results might not be comparable to mechanisms in diurnal humans (Challet 2007). Using diurnal rodent animal models could be beneficial in this field of research (Ashkenazy et al 2009; Bilu et al 2016; Einat et al 2006; Leach et al 2013). Nevertheless, effects are quite robust as various disruptions of one gene (i.e., Clock ) as well as targeting related pathways or environmentally influence sleeping behavior result in similar effects (McClung et al 2005; Mukherjee et al 2010; Prickaerts et al 2006; Roybal et al 2007).…”

Chronic Stress May Not Be a Factor in the Behavioral Response to Chronic Lithium in ICR Mice

“…In the current experiment, environmental enrichment included materials that enabled the building of a somewhat shaded nest by the mice. (3) It had been suggested that the sensitivity to light manipulations is higher and more consistent in diurnal animals compared with nocturnal ones [27][28][29], whereas the current study used nocturnal mice.…”