Prolactin (PRL) promotes and coordinates the various physiological and behavioral changes that are necessary for successful parental care in vertebrates. Although the effects of PRL on peripheral target organs that serve parental functions have been studied in some depth, much less is known about how PRL acts directly or indirectly on the brain to induce parental behavior and associated neuroendocrine changes, such as reduced gonadal activity. This proposal employs a powerful avian model, the ring dove (Streptopelia risoria), to explore these effects in detail. The proposed studies build on our previous work to 1) characterize the neurochemical events that mediate these changes and 2) identify key components of the neural circuitry involved. Neurochemical investigations will evaluate neuropeptide Y (NPY) and adrenal glucocorticoids as potential mediators of PRL-induced parental hyperphagia (feeding) and gonadal suppression. These studies will examine the effects of intracerebroventricular (ICV) injections of these compounds and measure changes in NPY gene expression and protein in response to PRL or glucocorticoid injection. They will also determine if these PRL-induced changes are attenuated by blocking NPY or glucocorticoid action. Studies of possible GnRH mediation of PRL-induced gonadal suppression and dopamine involvement in PRL-induced parental hyperphagia are also proposed. Neuroanatomical investigations will use immunocytochemical detection of immediate-early gene products to identify neurons that are activated in response to ICV injection of PRL, NPY, and glucocorticoids, to visualize the pattern of neuronal activation associated with parental interactions with young, and to determine how the pattern changes in response to PRL and previous parental experience. These studies contribute to the long term objective of obtaining an integrated picture of how PRL influences brain function and behavior in a parental context. They will also increase our limited understanding of how adenohypophyseal hormones influence brain activity and provide new insights into the causes of infertility, energy balance, and behavioral alterations that are associated with hyperprolactinemia in the clinical setting.
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