The medial preoptic area of the hypothalamus is known to exhibit sexual dimorphism in a number of mammalian systems, including humans. Moreover, sex differences have been revealed in several neurochemical systems, including the endogenous opioid peptides and their receptors. Evidence suggests that hypothalamic opioid peptides influence neuroendocrine physiology and behavior. Dr. Hammer will examine the regulation of brain opioid peptide and receptor systems by gonadal steroid hormones in identified neuronal circuits of the hypothalamus. Using state-of-the-art neuroanatomical and molecular biological techniques, he will describe and characterize changes in the regulation of opiate receptor expression in specific brain regions and neurons during estrus. After determining the precise localization of these receptors, which are the functional site of action for opioid peptides, he will identify the various populations of opioid neurons that project to this important hypothalamic region. These studies will provide novel information about the anatomy and steroid sensitivity of opioid hypothalamic circuits. The results will lead to a greater understanding of the basic mechanisms underlying the control of neuroendocrine function, and how disruption of this mechanism by aberrant hormonal or narcotic action could produce reproductive or other neuroendocrine disorders.
