This thesis investigates the role of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in mood disorders, particularly major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SCZ), as well as in Alzheimer's disease (AD). Given the high prevalence and significant impact of these disorders, understanding the underlying biological mechanisms is critical for improving treatment outcomes. The thesis extensively explores the distribution and implications of PACAP expression in the human brain, focusing on its association with the hypothalamic-pituitary-adrenal (HPA) axis, which plays a crucial role in stress response and mood regulation. Through a comprehensive analysis combining immunocytochemical staining, in situ hybridization, and quantitative PCR, the research elucidates the differential expression of PACAP in various brain regions of the hypothalamus and prefrontal cortex. Notably, it highlights increased PACAP expression in the paraventricular nucleus (PVN) and the central nucleus of the bed nucleus of the stria terminalis (cBNST) in mood disorder patients, indicating a potential role in the heightened stress response associated with these conditions. Importantly, the study uncovers a significant association between increased PACAP expression and suicide in individuals with mood disorders or SCZ, suggesting a potential link between PACAP dysregulation and suicidal behaviors. The research also delves into sex differences in PACAP expression, revealing variations that may contribute to the observed higher vulnerability of women to stress-related disorders. These findings underscore the complexity of PACAP's role in the brain's stress and mood regulation mechanisms and its potential as a biomarker for mood disorders, depression in AD, and suicidal risk. By providing novel insights into the role of PACAP in neuropsychiatric and neurodegenerative diseases, and its specific association with suicidal behavior and sex differences, this thesis contributes to the ongoing search for targeted, effective interventions for individuals affected by these debilitating conditions, especially those at risk of suicide.
|