Neuropeptide Signaling Networks and Brain Circuit Plasticity

Signaling mechanisms underlying activity-dependent integration of adult-born neurons in the mouse olfactory bulb

Adult neurogenesis has fascinated the field of neuroscience for decades given the prospects of harnessing mechanisms that facilitate the rewiring and/or replacement of adult brain tissue. The subgranular zone of the hippocampus and the subventricular zone of the lateral ventricle are the two main areas in the brain that exhibit ongoing neurogenesis. Of these, adult-born neurons within the olfactory bulb have proven to be a powerful model for studying circuit plasticity, providing a broad and accessible avenue into neuron development, migration, and continued circuit integration within adult brain tissue. This review focuses on some of the recognized molecular and signaling mechanisms underlying activity-dependent adult-born neuron development. Notably, olfactory activity and behavioral states contribute to adult-born neuron plasticity through sensory and centrifugal inputs, in which calcium-dependent transcriptional programs, local translation, and neuropeptide signaling play important roles. This review also highlights areas of needed continued investigation to better understand the remarkable phenomenon of adult-born neuron integration.

Eating disorder animal model

PURPOSE OF REVIEW

The aim of this review is to describe animal models that simulate the features of eating disorders. The literature pertaining to animal models that are of relevance for clinical eating disorders and the possible underpinning mechanisms was reviewed using PubMed, Ovid database and Google Scholar.

RECENT FINDINGS

New refinements of the circuits regulated by neurotransmitters and neuropeptides which instigate eating behaviours and the various feedback pathways which monitor acute and chronic nutrient status continue to be discovered. Moreover, work with the animal models that simulate the behavioural features and risk factors related to eating disorders is flourishing and providing new insights into possible causal mechanisms. For example, rodents develop binge-eating behaviours if they are intermittently exposed to processed, palatable foods and/or sugar adulterated drinks. This led to the controversial conceptualization of binge eating as a form of food addiction. Self-starvation taken to a fatal consequence such as occurs in anorexia nervosa can emerge in rodents exposed to triggers like social exclusion and/or the opportunity to exercise.

SUMMARY

There are plausible animal models for both anorexia nervosa and binge-eating disorders. These can be used to elaborate the theoretical models to explain the mechanisms underpinning eating disorders.

Characterizing the Molecular Architecture of Cortical Regions Associated with High Educational Attainment in Older Individuals

Neuroimaging investigations have revealed interindividual variations in anatomy, metabolism, activity, and connectivity of specific cortical association areas through which years of education (YoE), as a common proxy of cognitive reserve, may operate in the face of age- or pathology-associated brain changes. However, the associated molecular properties of YoE-related brain regions and the biological pathways involved remain poorly understood. In the present study we first identified brain areas that showed an association between cortical thickness and YoE among 122 cognitively healthy older human individuals (87 female). We subsequently characterized molecular properties of these regions by studying brain-wide microarray measurements of regional gene expression. In accordance with previous studies, we observed that YoE were associated with higher cortical thickness in medial prefrontal, anterior cingulate, and orbitofrontal areas. Compared with the rest of the cortex, these regions exhibited a distinct gene expression profile characterized by relative upregulation of gene sets implicated in ionotropic and metabotropic neurotransmission as well as activation of immune response. Our genome-wide expression profile analysis of YoE-related brain regions points to distinct molecular pathways that may underlie a higher capacity for plastic changes in response to lifetime intellectual enrichment and potentially also a higher resilience to age-related pathologic brain changes.SIGNIFICANCE STATEMENT We combined a neuroimaging-based analysis with a transcriptome-wide gene expression approach to investigate the molecular-functional properties of cortical regions associated with educational attainment, as a commonly used proxy for cognitive reserve, in older individuals. The strongest association with education was observed in specific areas of the medial prefrontal cortex, and these areas exhibited a distinct gene expression profile characterized by relative upregulation of gene sets implicated in neurotransmission and immune responses. These findings complement previous neuroimaging studies in the field and point to novel biological pathways that may mediate the beneficial effects of high educational attainment on adaptability to cope with, or prevent, age-related brain changes. The identified genes and pathways now warrant further exploration in mechanistic studies.