Integration of Stress and Reproductive Axes by Dopamine

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DESCRIPTION (provided by applicant): Our overall goal is to determine how the stress response system and the reproductive system interact. This proposal is based on our observation that dopamine neurons in the medial zona incerta (MZI) are sensitive to variations in circulating adrenal steroid levels. These neurons are known to regulate reproductive and feeding behavior but have not previously been implicated in the stress response. However, these neurons are believed to project to corticotropin releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) and are thus in a position to regulate hypothalamic-pituitary-adrenal (HPA) axis activity, which is increased during stress. We hypothesize that activity of MZI dopamine neurons leads to dopamine release in the PVN and that this simultaneously stimulates reproductive behavior and inhibits the stress response. Furthermore, we hypothesize that this activity is sensitive to glucocorticoid levels, which increase during stress. In specific aim one we will determine if dopamine system transcripts within the MZI are regulated by glucocorticoids and, if so, which ones. This will be accomplished by combining laser- capture microscopy (LCM), to isolate MZI neurons, with quantitative real-time PCR (qRT-PCR) to measure dopamine transcript levels in adrenalectomized rats. In specific aim two we will determine which dopamine receptors are expressed in the PVN and specifically, which, if any, are expressed on CRH neurons. This will also be accomplished by combining LCM of PVN neurons with qRT-PCR followed by double-labeled in situ hybridization. In specific aim three we will inject a dopamine agonist into the PVN and determine the effect of this manipulation on markers of HPA activation, namely, increases in serum adrenocorticotropin hormone and corticosterone. For these studies rats will be cannulated to allow injection into the PVN just prior to either handling or restraint stress. The studies are important to human health because they will help elucidate the function of dopamine activity in the PVN and the factors that regulate this activity. This is relevant because several clinically used drugs that treat conditions as varied as psychosis, sexual dysfunction and Parkinson's disease manipulate brain dopamine and the consequences of this manipulation on stress and HPA activity is not understood.