Early alterations in the MCH system link aberrant neuronal activity and sleep disturbances in a mouse model of Alzheimer's disease.

Early Alzheimer's disease (AD) is associated with hippocampal hyperactivity and decreased sleep quality. Here we show that homeostatic mechanisms transiently counteract the increased excitatory drive to CA1 neurons in AppNL-G-F mice, but that this mechanism fails in older mice. Spatial transcriptomics analysis identifies Pmch as part of the adaptive response in AppNL-G-F mice. Pmch encodes melanin-concentrating hormone (MCH), which is produced in sleep-active lateral hypothalamic neurons that project to CA1 and modulate memory. We show that MCH downregulates synaptic transmission, modulates firing rate homeostasis in hippocampal neurons and reverses the increased excitatory drive to CA1 neurons in AppNL-G-F mice. AppNL-G-F mice spend less time in rapid eye movement (REM) sleep. AppNL-G-F mice and individuals with AD show progressive changes in morphology of CA1-projecting MCH axons. Our findings identify the MCH system as vulnerable in early AD and suggest that impaired MCH-system function contributes to aberrant excitatory drive and sleep defects, which can compromise hippocampus-dependent functions

TEMPERAMENT AND CHARACTER TRAITS IN PATIENTS WITH CONVERSION DISORDER AND THEIR RELATIONS WITH DISSOCIATION

Background: The purpose of this study was to investigate temperament and character traits in patients with conversion disorder and the relation of these traits with dissociative symptoms. Subjects and methods: Sixty patients (60) diagnosed with conversion disorder according to DSM-IV-TR and 60 healthy volunteers were included in the study. All participants’ temperament and character traits were determined using Cloninger’s Temperament and Character Inventory (TCI). Patients with conversion disorder were divided into two subgroups using the Dissociative Experiences Scale (DES), dissociative (n=30, 50%) and non-dissociative (n=30, 50%). The two conversion disorder subgroups were compared with the control group in terms of temperament and character traits. Correlation analysis was also performed between TCI and DES scores in the entire conversion group. Results: Novelty seeking (NS) scores were lower in both the dissociative and non-dissociative groups compared to the control group. Harm avoidance (HA) scores were higher in the dissociative group than in the control group. Reward dependence (RD) scores were lower in the dissociative group than in the non-dissociative and control group. Self-directedness (SD) scores were lower in the dissociative group than in the control group. Self-transcendence (ST) scores were higher in the dissociative group than in the non-dissociative group. DES scores were negatively correlated with RD and SD scores in the entire conversion group and positively correlated with ST scores. Conclusions: Low NS temperament traits may be associated with conversion disorder. High HA and low RD temperament traits and low SD and high ST character traits may be associated with pathological dissociation in patients with conversion disorder

GAZIANTEP UNIVERSITY

Muhsin Hazar Murat Ağarı Mürsel Biçer Necmi Emel Dilmen Neşe Kars Tayanç Özden Demir Recep Dündar Rüstem Yanar Salih Yeşil Serap Durukan Köse Seyhan Taş Zekiye Antakyalıoğl