This proposal for a Mentored Scientist Development Award focuses on elucidating the role of beta adrenergic receptors (ARs) and the adenylyl cyclase-cyclic cAMP (AC-cAMP) pathway in the pathophysiology of depression and suicide. Several studies suggest that betaAR number is increased in the postmortem brain of suicide subjects; however, the precise mechanism, significance and the cellular/molecular nature of events associated with this increase have not been elucidated. The goals of this study are to examine: 1) if upregulation of betaARs is due to increased rnRNA and/or protein expression of beta1 and/or beta2 ARs; 2) whether this increase is associated with increase transcription rate and/or dysregulated HPA axis; 3) functional consequences of increased betaARs in the AC-cAMP signaling pathway at the level of catalytic and regulatory activities of protein kinase A (PKA) and gene transcription of their specific subunits; 4) functional significance of altered PKA by examining functional characteristics and gene expression of transcription factors and target genes; 5) the localization of these changes at the cellular level in discrete brain areas; and 5) whether these changes are specific to depression.To achieve these goals we propose a series of related human postmortem brain and animal studies. We will study mRNA and protein expression of beta1 and beta2ARs by quantitative RT-PCR, in-situ hybridization and gold-immunolabeling. To examine whether changes in betaARs are associated with alterations in components of the AC- cAMP signaling pathway, we will study [3H]cAMP binding to PKA; total, endogenous and betaAR-mediated PKA activity; mRNA and protein expression of PKA (regulatory and catalytic subunits), CREB, BDNF and phospho-CREB; CREB-DNA binding activity in BAs 8, 9, 10 and hippocampus of suicide victims and age-, postmortem interval-, and gender-matched nonpsychiatric control subjects. We will examine changes in mRNA and protein expression in discrete areas of the brain (layers I-VI of prefrontal cortex and areas CA1-4, dentate gyrus subiculum and area entorhinalis of the hippocampal formation). Further, to examine if the changes in the proposed measures are specific to depression, we will examine the effects of major depression on the proposed measures. To consolidate our human postmortem brain findings, we will study the proposed measures in prefrontal cortex and hippocampus of behaviorally depressed rats. Finally, to examine if these changes are associated with abnormal HPA function we will study the proposed measures in prefrontal cortex and hippocampus of corticosterone-treated rats with and without adrenalectomy. With this proposal the candidate seeks training in 1) Clinical and psychological aspects of mental disorders and suicide, 2) molecular biology, 3) neuroanatomy, 4) animal behavior, and 5) specialized statistical analyses. The rigorous training plan, which integrates strong didactics and multidisciplinary expertise, and the research plan will advance the knowledge of molecular mechanisms associated with depression and suicide and will provide the candidate with the skills needed to achieve independence in this highly complex field.
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