The brain CRH system plays a prominent role in integrating the responses to stress. Dysregulation of the CRH system has been implicated in stress-related psychopathologies such as depression and anxiety. CRH and related ligands mediate their effects through at least two receptors, R1 and R2a. While R1 has been clearly linked to stress and psychopathology, little is known regarding the function of R2a. The proposed studies will extend our earlier work implicating the amygdala CRH system in regulating stress-related effects. We will now explore the contributions of CRH receptor subtypes in mediating stress-induced responses. Our preliminary data strongly suggest that lateral septum (LS) R2a mediates fear-related behavior. We will therefore explore the hypothesis that R2a in the LS and R1 in the central nucleus of the amygdala work together to mediate adaptive fear-related behaviors. Little is known about the mechanisms by which stress influences critical intracellular signaling pathways. Because phosphorylation of the transcription factor CREB is a common step in many intracellular signaling pathways, we will use an ethologically relevant psychological stressor to determine the extent to which stress-induced R1 and R2a activation mediates effects on CREB phosphorylation. Additionally, using specific protein kinase inhibitors, we will determine which protein kinases are involved in mediating the acute behavioral effects of CRH. To link these data to psychopathology, we will characterize changes in CRH receptors and CREB and pCREB in rats that fail to adapt behaviorally to chronic stress exposure. In addition, to explore new treatment strategies for stress-related psychopathology, rats that display maladaptive behavioral responses will be treated with viral vectors expressing R1 or R2a antisense constructs to continuously reduce either R1 or R2a. It is predicted that antisense producing viral vectors will reduce stress-like responses in these rats. Finally, to directly explore changes in CRH and CREB in relation to human psychopathology, we will characterize CRH receptors and CREB mRNA in postmortem amygdala samples from unipolar depressed, bipolar, and schizophrenic subjects. Overall, these studies will provide important new insights into the role of R2a, interactions between R1 and R2a in adaptive and maladaptive fear responses, intracellular changes underlying these responses, and alterations in the CRH system and CREB associated with human psychopathology.
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