The study of the genetics of complex behaviors has evolved dramatically from the days of the nature versus nurture debates that dominated much of the past century. Here we discuss advances in our understanding of the genetics of affective and anxiety disorders. In particular, we highlight our growing understanding of specific gene-environment interactions that occur during critical periods in development, setting the stage for later behavioral phenotypes. We review the recent literature in the field, focusing on recent advances in our understanding of the role of the serotonin system in establishing normal anxiety levels during development. We emphasize the importance of understanding the effect of genetic variation at the level of functional circuits and provide examples from the literature of how such an approach has been exploited to study novel genetic endpoints, including genetically based variation in response to medication, a potentially valuable phenotype that has not received much attention to date.
"The central serotonin (5-HT) system is known to be involved in emotion, learning and memory (Barnes and Sharp, 1999; Duman and Voleti, 2012), and 5-HT deficiency in the brain is believed to be a major causative factor in anxiety and depression (Brigitta, 2002; Leonardo and Hen, 2006). Selective 5-HT reuptake inhibitors (SSRIs), which can promote monoamine system functions, attenuate anxiety-like behaviors (Graeff et al., 1996) and also produce certain beneficial effects in patients with depression (Artigas et al., 1996; Blier and Ward, 2003). "
[Show abstract][Hide abstract] ABSTRACT: Dysfunction of central serotonin (5-HT) system has been proposed to be one of the underlying mechanisms for anxiety and depression, and the association of diabetes mellitus and psychiatric disorders has been noticed by the high prevalence of anxiety/depression in patients with diabetes mellitus. This promoted us to examine these behaviors in central 5-HT-deficient mice and those also suffering with diabetes mellitus. Mice lacking either 5-HT or central serotonergic neurons were generated by conditional deletion of Tph2 or Lmx1b respectively. Simultaneous depletion of both central serotonergic neurons and pancreatic islet cells was achieved by administration of diphtheria toxin (DT) in Pet1-Cre;Rosa26-DT receptor (DTR) mice. The central 5-HT-deficient mice showed reduced anxiety-like behaviors as they spent more time in and entered more often into the light box in the light/dark box test compared with controls; similar results were observed in the elevated plus maze test. However, they displayed no differences in the immobility time of the forced swimming and tail suspension tests suggesting normal depression-like behaviors in central 5-HT-deficient mice. As expected, DT-treated Pet1-Cre;Rosa26-DTR mice lacking both central serotonergic neurons and pancreatic islet endocrine cells exhibited several classic diabetic symptoms. Interestingly, they displayed increased anxiety-like behaviors but reduced immobility time in the forced swimming and tail suspension tests. Furthermore, the hippocampal neurogenesis was dramatically enhanced in these mice. These results suggest that the deficiency of central 5-HT may not be sufficient to induce anxiety/depression-like behaviors in mice, and the enhanced hippocampal neurogenesis may contribute to the altered depression-like behaviors in the 5-HT-deficient mice with diabetes. Our current investigation provides understanding the relationship between diabetes mellitus and psychiatric disorders.
"Importantly, these manipulations result in models of both anxiety and depression. While anxiety and depression are generally conceived of as distinct psychiatric disorders, they have a high comorbidity with co-occurrence rates up to 60% in patients (Gorman, 1996; Leonardo and Hen, 2006). Ultimately, given that depression is a highly heterogenous disease, no one animal model will accurately replicate the various combinations of phenotypes that are seen in depression. "
[Show abstract][Hide abstract] ABSTRACT: Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders and non-responders to treatment. Delineation of these mechanisms largely relies on experiments that utilize animal models. Therefore, this review provides an overview of the various mouse models that are currently used to assess the antidepressant response, such as chronic mild stress, social defeat, and chronic corticosterone. We discuss how these mouse models can be used to advance our understanding of the differences between responders and non-responders to antidepressant treatment. We also provide an overview of experimental treatment modalities that are used for treatment-resistant depression, such as deep brain stimulation and ketamine administration. We will then review the various genetic polymorphisms and transgenic mice that display resistance to antidepressant treatment. Finally, we synthesize the published data to describe a potential neural circuit underlying the antidepressant response and treatment resistance.
Available from: Danica Zmejkoski (former Dimitrijevic)
"In this study we also showed that ELF magnetic fi eld exposure at this developmental stage decreases locomotor activity of three-day-old fl ies. Due to the ELF magnetic fi eld exposure at the time of brain development, when the activation of serotonin receptors begins, later reduced locomotor activity may be linked with a possible impact of magnetic fi eld on serotonergic transmission in the brain (Leonardo and Hen 2006). It is well known that serotonin has a role in response to stimuli from environment (Heym et al. 1982, Waterhouse et al. 2004) and that serotonergic neurons are sensitive to changes in behavioral activation (Grahn et al. 1999, Jacobs and Fornal 1999, Portas et al. 2000, Abrams et al. 2004). "
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Extremely low frequency (ELF) magnetic fields are essential ecological factors which may induce changes in many organisms. The aim of this study was to examine the effects in Drosophila subobscura exposed for 48 h to ELF magnetic field (50 Hz, 0.5 mT) at different developmental stages.
Materials and methods:
Egg-first instar larvae developmental stage of D. subobscura isofemale lines was exposed to ELF magnetic field, and fitness components (developmental time, developmental dynamics, viability and sex ratio) and locomotor activity of three-day-old males and females were monitored. Also, just eclosed D. subobscura isofemale adults were exposed to ELF magnetic field and their locomotor activity was monitored just after.
ELF magnetic field shortens developmental time, increases viability and does not affect sex ratio of D. subobscura. No matter which developmental stage is exposed, ELF magnetic field significantly decreases locomotor activity of adult flies, but after exposure of just eclosed adults observed change lasts longer.
Applied ELF magnetic field modifies fitness components and locomotor activity of D. subobscura. Observed effects can be attributed to the influence of magnetic field on different stages of development where the hormonal and nervous systems play important role in the control of examined parameters.
International Journal of Radiation Biology 01/2014; 90(5). DOI:10.3109/09553002.2014.888105 · 1.69 Impact Factor
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