Male reproductive function is under the control of a region of the brain called the medial preoptic area. Within that area several neurotransmitters and their interactions modulate that function. In this award, Dr. Elaine Hull will study the effects of direct injections of neurotransmitter substances into the medial preoptic area as well as the endogenous levels of these substances in the same region. The technique used to collect fluid bathing the brain tissue is microdialysis and the technique used to measure the levels of the neurotransmitters is high performance liquid chromatography. Both of these techniques are very sensitive to the small amounts of neurotransmitters that are normally present within brain tissue. Behavioral observations will be made in order to determine which neurotransmitters are released during reproductive behavior. The neurotransmitters studied will be serotonin, dopamine, and gamma-aminobutyric acid. This will provide information about the biochemical messages that control reproductive function. The knowledge gained in these studies will contribute to understanding how the brain controls complex functions, such as reproduction.