Jennifer M. Swann - US grants

Dr. Swann will carry out experiments desdesigned to determine how sex steroids influence the activity of neural cells that regulate behavior. Gonadal steroids have profound effects on the organization and expression of almost all forms of behavior. Although it is clear from several different approaches that steroids affect behavior through actions on specific neuronal cell groups, the exact way in which steroids change neuronal function is not known. The results from several experiments in Dr. Swann's lab indicate that gonadal steroids may regulate behavior by regulating neuronal activity and communication among three central areas in the hypothalamus (a brain structure). These results were discovered by indirectly monitoring neuronal activity using a novel technique. Dr. Swann plans to confirm and expand these findings by directly monitoring neuronal activity in the same experimental design. Direct recording of neuronal activity is a laborious technique that requires substantial technical skill and equipment. Therefore, Dr. Swann had planned to visit laboratories with special expertise in this technique. These plans were delayed by the birth of her daughter. The POWRE award will provide the funds necessary to complete these experiments, allow Dr. Swann to catch up on time lost to maternity, and prepare her for a new phase of research using cutting-edge neuronal monitoring techniques.

Several behaviors are differentially expressed in male and female mammals as adults, typically regulated by the levels of steroid hormones that were present during early postnatal development. A number of differences in the brain also have been correlated with sex differences in behavior, including differences in numbers and density of particular nuclei (clusters of nerve cells) in parts of the brain. Changes in these neural parameters suggest that changes also are required in the afferent and efferent neural connections of these nuclei. This project combines hormonal treatments with quantitative neuroanatomy to test the hypothesis that neonatal steroids regulate male sexual behavior by regulating the development of the number, density, and interconnections of neurons in the magnocellular part of the medial preoptic nucleus (MPN mag), which is involved in olfactory-driven male sexual behavior.
This study provides a unique opportunity to clarify functional roles of neuronal differences in sexually dimorphic structures in the brain, and will be important for future molecular studies underlying dimorphic neurogenesis, so the impact will extend to developmental biology. In addition, the broader impact promotes research by a woman investigator from an underrepresented group, who is actively involved in increasing the representation of minority students in scientific research.

This Research Experience for Undergraduates (REU) Site is co-funded by the Department of Defense in partnership with the NSF REU program. This award provides support for an REU Site at Lehigh University. Ten rising sophomores (i.e. students that have completed the freshman year but have not started the sophomore year) will spend 12 weeks in the summer engaged in research in neuroscience and robotics. This unique interdisciplinary program will expose students majoring in mechanical engineering and students majoring in the biological sciences to fundamental concepts in both academic disciplines. It is anticipated that this program will impact the nations' need to increase the number of U.S. citizens and permanent residents prepared for research-related careers, in addition to impacting the need to increase the number of U.S. citizens from population groups underrepresented in science and engineering that are engaged in research-related careers.

Steroids exert dramatic, highly reproducible effects on behavior in every species studied to date from insects to man. Behavioral changes are strongly correlated with structural and functional changes in the connections among the cells in the brain, or synapses in the adult brain. Gonadal steroids such as testosterone have been shown to accelerate and induce changes in the strength and number of synapses in areas responsible for learning and memory. The goal of this project is to determine if the presence or absence of testosterone changes synaptic strength among nerve cells in a neural network responsible for social and reproductive behaviors in adults. Synapses will be identified with the latest technology and examined under low and high power microscopes to identify significant changes in the number, function, and source of synapses in the preoptic area, an important integrating structure in this network. Results from these studies will enhance our understanding of the role of gonadal steroids in the regulation of neural function in the adult brain, thus setting the stage for future studies of growth enhancing chemicals and substrates involved in sexual differentiation, aging and injury. This project will offer unique training opportunites in neuroanatomy and will include undergraduates and graduates in the collection, analysis and processing of the results.